chore(backend): satisfy cargo fmt and clippy --all-targets

- Apply rustfmt diffs in claude_desktop_config.rs
- Allow needless_return on current_platform_paths (cfg-mirrored arms)
- Allow too_many_arguments on RequestForwarder::forward
- Replace `let mut + reassign` with struct literals in tests
  (settings, backup, provider, response_processor)
- Use Path::new instead of PathBuf::from to fix cmp_owned in misc tests
- Replace 3.14 with 3.5 in config test to avoid approx_constant lint

src-tauri/src/claude_desktop_config.rs

@@ -586,15 +586,12 @@ pub fn map_proxy_request_model(mut body: Value, provider: &Provider) -> Result<V
         })?;
 
     let routes = proxy_model_routes(provider)?;
-    let route = routes
-        .iter()
-        .find(|r| r.route_id == requested)
-        .or_else(|| {
-            let base = strip_one_m_context_suffix(&requested);
-            routes
-                .iter()
-                .find(|r| strip_one_m_context_suffix(&r.route_id) == base)
-        });
+    let route = routes.iter().find(|r| r.route_id == requested).or_else(|| {
+        let base = strip_one_m_context_suffix(&requested);
+        routes
+            .iter()
+            .find(|r| strip_one_m_context_suffix(&r.route_id) == base)
+    });
     let Some(route) = route else {
         return Err(AppError::localized(
             "claude_desktop.provider.route_unknown",
@@ -628,7 +625,9 @@ fn apply_provider_to_paths(
     }
 
     validate_provider(provider)?;
-    with_rollback(paths, |paths| apply_provider_to_paths_inner(db, provider, paths))
+    with_rollback(paths, |paths| {
+        apply_provider_to_paths_inner(db, provider, paths)
+    })
 }
 
 fn restore_official_at_paths(paths: &ClaudeDesktopPaths) -> Result<(), AppError> {
@@ -645,9 +644,7 @@ where
         Err(err) => match restore_snapshots(&snapshots) {
             Ok(()) => Err(err),
             Err(rollback_err) => {
-                log::error!(
-                    "Failed to rollback Claude Desktop config after error: {rollback_err}"
-                );
+                log::error!("Failed to rollback Claude Desktop config after error: {rollback_err}");
                 Err(AppError::Message(format!(
                     "{err}; rollback failed: {rollback_err}"
                 )))
@@ -894,6 +891,7 @@ fn is_supported_platform() -> bool {
     cfg!(any(target_os = "macos", windows))
 }
 
+#[allow(clippy::needless_return)]
 fn current_platform_paths() -> Result<ClaudeDesktopPaths, AppError> {
     #[cfg(target_os = "macos")]
     {

src-tauri/src/commands/misc.rs

@@ -1591,7 +1591,7 @@ pub async fn set_window_theme(window: tauri::Window, theme: String) -> Result<()
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::path::PathBuf;
+    use std::path::{Path, PathBuf};
 
     #[test]
     fn test_extract_version() {
@@ -1679,7 +1679,7 @@ mod tests {
 
         let count = paths
             .iter()
-            .filter(|path| **path == PathBuf::from("/same/path"))
+            .filter(|path| path.as_path() == Path::new("/same/path"))
             .count();
         assert_eq!(count, 1);
     }
@@ -1691,7 +1691,7 @@ mod tests {
 
         let count = paths
             .iter()
-            .filter(|path| **path == PathBuf::from("/home/tester/.bun/bin"))
+            .filter(|path| path.as_path() == Path::new("/home/tester/.bun/bin"))
             .count();
         assert_eq!(count, 1);
     }

src-tauri/src/commands/settings.rs

@@ -87,13 +87,15 @@ mod tests {
 
     #[test]
     fn save_settings_should_preserve_existing_webdav_when_payload_omits_it() {
-        let mut existing = AppSettings::default();
-        existing.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.example.com".to_string(),
-            username: "alice".to_string(),
-            password: "secret".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let existing = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.example.com".to_string(),
+                username: "alice".to_string(),
+                password: "secret".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
         let incoming = AppSettings::default();
         let merged = merge_settings_for_save(incoming, &existing);
@@ -107,21 +109,25 @@ mod tests {
 
     #[test]
     fn save_settings_should_keep_incoming_webdav_when_present() {
-        let mut existing = AppSettings::default();
-        existing.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.old.example.com".to_string(),
-            username: "old".to_string(),
-            password: "old-pass".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let existing = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.old.example.com".to_string(),
+                username: "old".to_string(),
+                password: "old-pass".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
-        let mut incoming = AppSettings::default();
-        incoming.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.new.example.com".to_string(),
-            username: "new".to_string(),
-            password: "new-pass".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let incoming = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.new.example.com".to_string(),
+                username: "new".to_string(),
+                password: "new-pass".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
         let merged = merge_settings_for_save(incoming, &existing);
 
@@ -137,22 +143,26 @@ mod tests {
     /// must NOT overwrite the existing one.
     #[test]
     fn save_settings_should_preserve_password_when_incoming_has_empty_password() {
-        let mut existing = AppSettings::default();
-        existing.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.example.com".to_string(),
-            username: "alice".to_string(),
-            password: "secret".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let existing = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.example.com".to_string(),
+                username: "alice".to_string(),
+                password: "secret".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
         // Simulate frontend sending settings with cleared password
-        let mut incoming = AppSettings::default();
-        incoming.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.example.com".to_string(),
-            username: "alice".to_string(),
-            password: "".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let incoming = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.example.com".to_string(),
+                username: "alice".to_string(),
+                password: "".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
         let merged = merge_settings_for_save(incoming, &existing);
 
@@ -167,21 +177,25 @@ mod tests {
     /// work without panicking and keep the empty state.
     #[test]
     fn save_settings_should_handle_both_empty_passwords() {
-        let mut existing = AppSettings::default();
-        existing.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.example.com".to_string(),
-            username: "alice".to_string(),
-            password: "".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let existing = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.example.com".to_string(),
+                username: "alice".to_string(),
+                password: "".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
-        let mut incoming = AppSettings::default();
-        incoming.webdav_sync = Some(WebDavSyncSettings {
-            base_url: "https://dav.example.com".to_string(),
-            username: "alice".to_string(),
-            password: "".to_string(),
-            ..WebDavSyncSettings::default()
-        });
+        let incoming = AppSettings {
+            webdav_sync: Some(WebDavSyncSettings {
+                base_url: "https://dav.example.com".to_string(),
+                username: "alice".to_string(),
+                password: "".to_string(),
+                ..WebDavSyncSettings::default()
+            }),
+            ..AppSettings::default()
+        };
 
         let merged = merge_settings_for_save(incoming, &existing);
 

src-tauri/src/config.rs

@@ -342,7 +342,7 @@ mod tests {
         let cases = vec![
             serde_json::json!("hello"),
             serde_json::json!(42),
-            serde_json::json!(3.14),
+            serde_json::json!(3.5),
             serde_json::json!(true),
             serde_json::json!(null),
         ];

src-tauri/src/database/backup.rs

@@ -791,8 +791,10 @@ mod tests {
         std::fs::create_dir_all(&test_home).expect("create test home");
         std::env::set_var("CC_SWITCH_TEST_HOME", &test_home);
 
-        let mut settings = AppSettings::default();
-        settings.backup_interval_hours = Some(0);
+        let settings = AppSettings {
+            backup_interval_hours: Some(0),
+            ..AppSettings::default()
+        };
         update_settings(settings).expect("disable auto backup");
 
         let db = Database::memory()?;

src-tauri/src/provider.rs

@@ -760,8 +760,10 @@ mod tests {
 
     #[test]
     fn provider_meta_serializes_pricing_model_source() {
-        let mut meta = ProviderMeta::default();
-        meta.pricing_model_source = Some("response".to_string());
+        let meta = ProviderMeta {
+            pricing_model_source: Some("response".to_string()),
+            ..ProviderMeta::default()
+        };
 
         let value = serde_json::to_value(&meta).expect("serialize ProviderMeta");
 

src-tauri/src/proxy/forwarder.rs

@@ -764,6 +764,7 @@ impl RequestForwarder {
     }
 
     /// 转发单个请求（使用适配器）
+    #[allow(clippy::too_many_arguments)]
     async fn forward(
         &self,
         app_type: &AppType,

src-tauri/src/proxy/response_processor.rs

@@ -894,9 +894,11 @@ mod tests {
         db.set_pricing_model_source(app_type, "response").await?;
         seed_pricing(&db)?;
 
-        let mut meta = ProviderMeta::default();
-        meta.cost_multiplier = Some("2".to_string());
-        meta.pricing_model_source = Some("request".to_string());
+        let meta = ProviderMeta {
+            cost_multiplier: Some("2".to_string()),
+            pricing_model_source: Some("request".to_string()),
+            ..ProviderMeta::default()
+        };
         insert_provider(&db, "provider-1", app_type, meta)?;
 
         let state = build_state(db.clone());