Refactor/simplify proxy logs (#585)

* refactor(proxy): simplify logging for better readability

- Delete 17 verbose debug logs from handlers, streaming, and response_processor
- Convert excessive INFO logs to DEBUG level for internal processing details
- Add 2 critical INFO logs in forwarder.rs for failover scenarios:
  - Log when switching to next provider after failure
  - Log when all providers have been exhausted
- Fix clippy uninlined_format_args warning

This reduces log noise while maintaining visibility into key user-facing decisions.

* fix: replace unsafe unwrap() calls with proper error handling

- database/dao/mcp.rs: Use map_err for serde_json serialization
- database/dao/providers.rs: Use map_err for settings_config and meta serialization
- commands/misc.rs: Use expect() for compile-time regex pattern
- services/prompt.rs: Use unwrap_or_default() for SystemTime
- deeplink/provider.rs: Replace unwrap() with is_none_or pattern for Option checks

Reduces potential panic points from 26 to 1 (static regex init, safe).

* refactor(proxy): simplify verbose logging output

- Remove response JSON full output logging in response_processor
- Remove per-request INFO logs in provider_router (failover status, provider selection)
- Change model mapping log from INFO to DEBUG
- Change usage logging failure from INFO to WARN
- Remove redundant debug logs for circuit breaker operations

Reduces log noise significantly while preserving important warnings and errors.

* feat(proxy): add structured log codes for i18n support

Add error code system to proxy module logs for multi-language support:

- CB-001~006: Circuit breaker state transitions and triggers
- SRV-001~004: Proxy server lifecycle events
- FWD-001~002: Request forwarding and failover
- FO-001~005: Failover switch operations
- USG-001~002: Usage logging errors

Log format: [CODE] Chinese message
Frontend/log tools can map codes to any language.

New file: src/proxy/log_codes.rs - centralized code definitions

* chore: bump version to 3.9.1

* style: format code with prettier and rustfmt

* fix(ui): allow number inputs to be fully cleared before saving

- Convert numeric state to string type for controlled inputs
- Use isNaN() check instead of || fallback to allow 0 values
- Apply fix to ProxyPanel, CircuitBreakerConfigPanel,
  AutoFailoverConfigPanel, and ModelTestConfigPanel

* feat(pricing): support @ separator in model name matching

- Refactor model name cleaning into chained method calls
- Add @ to - replacement (e.g., gpt-5.2-codex@low → gpt-5.2-codex-low)
- Add test case for @ separator matching

* fix(proxy): improve validation and error handling in proxy config panels

- Add StopTimeout/StopFailed error types for proper stop() error reporting
- Replace silent clamp with validation-and-block in config panels
- Add listenAddress format validation in ProxyPanel
- Use log_codes constants instead of hardcoded strings
- Use once_cell::Lazy for regex precompilation

* fix(proxy): harden error handling and input validation

- Handle RwLock poisoning in settings.rs with unwrap_or_else
- Add fallback for dirs::home_dir() in config modules
- Normalize localhost to 127.0.0.1 in ProxyPanel
- Format IPv6 addresses with brackets for valid URLs
- Strict port validation with pure digit regex
- Treat NaN as validation failure in config panels
- Log warning on cost_multiplier parse failure
- Align timeoutSeconds range to [0, 300] across all panels

src-tauri/src/settings.rs

@@ -92,12 +92,9 @@ impl Default for AppSettings {
 }
 
 impl AppSettings {
-    fn settings_path() -> PathBuf {
+    fn settings_path() -> Option<PathBuf> {
         // settings.json 保留用于旧版本迁移和无数据库场景
-        dirs::home_dir()
-            .expect("无法获取用户主目录")
-            .join(".cc-switch")
-            .join("settings.json")
+        dirs::home_dir().map(|h| h.join(".cc-switch").join("settings.json"))
     }
 
     fn normalize_paths(&mut self) {
@@ -131,7 +128,9 @@ impl AppSettings {
     }
 
     fn load_from_file() -> Self {
-        let path = Self::settings_path();
+        let Some(path) = Self::settings_path() else {
+            return Self::default();
+        };
         if let Ok(content) = fs::read_to_string(&path) {
             match serde_json::from_str::<AppSettings>(&content) {
                 Ok(mut settings) => {
@@ -156,7 +155,9 @@ impl AppSettings {
 fn save_settings_file(settings: &AppSettings) -> Result<(), AppError> {
     let mut normalized = settings.clone();
     normalized.normalize_paths();
-    let path = AppSettings::settings_path();
+    let Some(path) = AppSettings::settings_path() else {
+        return Err(AppError::Config("无法获取用户主目录".to_string()));
+    };
 
     if let Some(parent) = path.parent() {
         fs::create_dir_all(parent).map_err(|e| AppError::io(parent, e))?;
@@ -193,14 +194,23 @@ fn resolve_override_path(raw: &str) -> PathBuf {
 }
 
 pub fn get_settings() -> AppSettings {
-    settings_store().read().expect("读取设置锁失败").clone()
+    settings_store()
+        .read()
+        .unwrap_or_else(|e| {
+            log::warn!("设置锁已毒化，使用恢复值: {e}");
+            e.into_inner()
+        })
+        .clone()
 }
 
 pub fn update_settings(mut new_settings: AppSettings) -> Result<(), AppError> {
     new_settings.normalize_paths();
     save_settings_file(&new_settings)?;
 
-    let mut guard = settings_store().write().expect("写入设置锁失败");
+    let mut guard = settings_store().write().unwrap_or_else(|e| {
+        log::warn!("设置锁已毒化，使用恢复值: {e}");
+        e.into_inner()
+    });
     *guard = new_settings;
     Ok(())
 }
@@ -209,7 +219,10 @@ pub fn update_settings(mut new_settings: AppSettings) -> Result<(), AppError> {
 /// 用于导入配置等场景，确保内存缓存与文件同步
 pub fn reload_settings() -> Result<(), AppError> {
     let fresh_settings = AppSettings::load_from_file();
-    let mut guard = settings_store().write().expect("写入设置锁失败");
+    let mut guard = settings_store().write().unwrap_or_else(|e| {
+        log::warn!("设置锁已毒化，使用恢复值: {e}");
+        e.into_inner()
+    });
     *guard = fresh_settings;
     Ok(())
 }