feat: complete stage 4 cleanup and code formatting

This commit completes stage 4 of the refactoring plan, focusing on cleanup
and optimization of the modernized codebase.

## Key Changes

### Code Cleanup
- Remove legacy `src/lib/styles.ts` (no longer needed)
- Remove old modal components (`ImportProgressModal.tsx`, `ProviderList.tsx`)
- Streamline `src/lib/tauri-api.ts` from 712 lines to 17 lines (-97.6%)
  - Remove global `window.api` pollution
  - Keep only event listeners (`tauriEvents.onProviderSwitched`)
  - All API calls now use modular `@/lib/api/*` layer

### Type System
- Clean up `src/vite-env.d.ts` (remove 156 lines of outdated types)
- Remove obsolete global type declarations
- All TypeScript checks pass with zero errors

### Code Formatting
- Format all source files with Prettier (82 files)
- Fix formatting issues in 15 files:
  - App.tsx and core components
  - MCP management components
  - Settings module components
  - Provider management components
  - UI components

### Documentation Updates
- Update `REFACTORING_CHECKLIST.md` with stage 4 progress
- Mark completed tasks in `REFACTORING_MASTER_PLAN.md`

## Impact

**Code Reduction:**
- Total: -1,753 lines, +384 lines (net -1,369 lines)
- tauri-api.ts: 712 → 17 lines (-97.6%)
- Removed styles.ts: -82 lines
- Removed vite-env.d.ts declarations: -156 lines

**Quality Improvements:**
- ✅ Zero TypeScript errors
- ✅ Zero TODO/FIXME comments
- ✅ 100% Prettier compliant
- ✅ Zero `window.api` references
- ✅ Fully modular API layer

## Testing
- [x] TypeScript compilation passes
- [x] Code formatting validated
- [x] No linting errors

Stage 4 completion: 100%
Ready for stage 5 (testing and bug fixes)

src/lib/api/mcp.ts

@@ -18,7 +18,7 @@ export const mcpApi = {
 
   async upsertServer(
     id: string,
-    spec: McpServerSpec | Record<string, any>
+    spec: McpServerSpec | Record<string, any>,
   ): Promise<boolean> {
     return await invoke("upsert_claude_mcp_server", { id, spec });
   },
@@ -35,11 +35,19 @@ export const mcpApi = {
     return await invoke("get_mcp_config", { app });
   },
 
+  async importFromClaude(): Promise<number> {
+    return await invoke("import_mcp_from_claude");
+  },
+
+  async importFromCodex(): Promise<number> {
+    return await invoke("import_mcp_from_codex");
+  },
+
   async upsertServerInConfig(
     app: AppType,
     id: string,
     spec: McpServer,
-    options?: { syncOtherSide?: boolean }
+    options?: { syncOtherSide?: boolean },
   ): Promise<boolean> {
     const payload = {
       app,
@@ -55,7 +63,7 @@ export const mcpApi = {
   async deleteServerInConfig(
     app: AppType,
     id: string,
-    options?: { syncOtherSide?: boolean }
+    options?: { syncOtherSide?: boolean },
   ): Promise<boolean> {
     const payload = {
       app,
@@ -66,4 +74,20 @@ export const mcpApi = {
     };
     return await invoke("delete_mcp_server_in_config", payload);
   },
+
+  async setEnabled(
+    app: AppType,
+    id: string,
+    enabled: boolean,
+  ): Promise<boolean> {
+    return await invoke("set_mcp_enabled", { app, id, enabled });
+  },
+
+  async syncEnabledToClaude(): Promise<boolean> {
+    return await invoke("sync_enabled_mcp_to_claude");
+  },
+
+  async syncEnabledToCodex(): Promise<boolean> {
+    return await invoke("sync_enabled_mcp_to_codex");
+  },
 };