feat: add Universal Provider feature (#348)

* feat: add Universal Provider feature

- Add Universal Provider data structures and type definitions
- Implement backend CRUD operations and sync functionality
- Add frontend UI components (UniversalProviderPanel, Card, FormModal)
- Add NewAPI icon and preset configuration
- Support cross-app (Claude/Codex/Gemini) configuration sync
- Add website URL field for providers
- Implement real-time refresh via event notifications
- Add i18n support (Chinese/English/Japanese)

* feat: integrate universal provider presets into add provider dialog

- Add universal provider presets (NewAPI, Custom Gateway) to preset selector
- Show universal presets with Layers icon badge in preset selector
- Open UniversalProviderFormModal when universal preset is clicked
- Pass initialPreset to auto-fill form when opened from add dialog
- Add i18n keys for addSuccess/addFailed messages
- Keep separate universal provider panel for management

* refactor: move universal provider management to add dialog

- Remove Layers button from main navigation header
- Add 'Manage' button next to universal provider presets
- Open UniversalProviderPanel from within add provider dialog
- Add i18n keys for 'manage' in all locales

* style: display universal provider presets on separate line

- Move universal provider section to a new row with border separator
- Add label '统一供应商:' to clarify the section

* style: unify universal provider label style with preset label

- Use FormLabel component for consistent styling
- Add background to 'Manage' button matching preset buttons
- Update icon size and button padding for consistency

* feat: add sync functionality and JSON preview for Universal Provider

* fix: add missing in_failover_queue field to Provider structs

After rebasing to main, the Provider struct gained a new
`in_failover_queue` field. This fix adds the missing field
to the three to_*_provider() methods in UniversalProvider.

* refactor: redesign AddProviderDialog with tab-based layout

- Add tabs to separate app-specific providers and universal providers
- Move "Add Universal Provider" button from panel header to footer
- Remove unused handleAdd callback and clean up imports
- Update emptyHint i18n text to reference the footer button

* fix: append /v1 suffix to Codex base_url in Universal Provider

Codex uses OpenAI-compatible API which requires the /v1 endpoint suffix.
The Universal Provider now automatically appends /v1 to base_url when
generating Codex provider config if not already present.

- Handle trailing slashes to avoid double slashes
- Apply fix to both backend (to_codex_provider) and frontend preview

* feat: auto-sync universal provider to apps on creation

Previously, users had to manually click sync after adding a universal
provider. Now it automatically syncs to Claude/Codex/Gemini on creation,
providing a smoother user experience.

---------

Co-authored-by: Jason <farion1231@gmail.com>

src-tauri/src/database/dao/mod.rs

@@ -10,6 +10,7 @@ pub mod proxy;
 pub mod settings;
 pub mod skills;
 pub mod stream_check;
+pub mod universal_providers;
 
 // 所有 DAO 方法都通过 Database impl 提供，无需单独导出
 // 导出 FailoverQueueItem 供外部使用

src-tauri/src/database/dao/universal_providers.rs

@@ -0,0 +1,75 @@
+//! 统一供应商 (Universal Provider) DAO
+//!
+//! 提供统一供应商的 CRUD 操作。
+
+use crate::database::{lock_conn, to_json_string, Database};
+use crate::error::AppError;
+use crate::provider::UniversalProvider;
+use std::collections::HashMap;
+
+/// 统一供应商的 Settings Key
+const UNIVERSAL_PROVIDERS_KEY: &str = "universal_providers";
+
+impl Database {
+    /// 获取所有统一供应商
+    pub fn get_all_universal_providers(&self) -> Result<HashMap<String, UniversalProvider>, AppError> {
+        let conn = lock_conn!(self.conn);
+        
+        let mut stmt = conn
+            .prepare("SELECT value FROM settings WHERE key = ?")
+            .map_err(|e| AppError::Database(e.to_string()))?;
+        
+        let result: Option<String> = stmt
+            .query_row([UNIVERSAL_PROVIDERS_KEY], |row| row.get(0))
+            .ok();
+        
+        match result {
+            Some(json) => {
+                serde_json::from_str(&json)
+                    .map_err(|e| AppError::Database(format!("解析统一供应商数据失败: {e}")))
+            }
+            None => Ok(HashMap::new()),
+        }
+    }
+
+    /// 获取单个统一供应商
+    pub fn get_universal_provider(&self, id: &str) -> Result<Option<UniversalProvider>, AppError> {
+        let providers = self.get_all_universal_providers()?;
+        Ok(providers.get(id).cloned())
+    }
+
+    /// 保存统一供应商（添加或更新）
+    pub fn save_universal_provider(&self, provider: &UniversalProvider) -> Result<(), AppError> {
+        let mut providers = self.get_all_universal_providers()?;
+        providers.insert(provider.id.clone(), provider.clone());
+        self.save_all_universal_providers(&providers)
+    }
+
+    /// 删除统一供应商
+    pub fn delete_universal_provider(&self, id: &str) -> Result<bool, AppError> {
+        let mut providers = self.get_all_universal_providers()?;
+        let existed = providers.remove(id).is_some();
+        if existed {
+            self.save_all_universal_providers(&providers)?;
+        }
+        Ok(existed)
+    }
+
+    /// 保存所有统一供应商（内部方法）
+    fn save_all_universal_providers(
+        &self,
+        providers: &HashMap<String, UniversalProvider>,
+    ) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+        let json = to_json_string(providers)?;
+        
+        conn.execute(
+            "INSERT OR REPLACE INTO settings (key, value) VALUES (?, ?)",
+            [UNIVERSAL_PROVIDERS_KEY, &json],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+        
+        Ok(())
+    }
+}
+