feat(frontend): implement comprehensive API Settings Management Interface

Implement a complete API Management Interface for React frontend with split-
panel layout, migrating all features from legacy JS frontend.

New Features:
- API Settings page with 5 tabs: Providers, Endpoints, Cache, Model Pools, CLI Settings
- Provider Management: CRUD operations, multi-key rotation, health checks, test connection
- Endpoint Management: CRUD operations, cache strategy configuration, enable/disable toggle
- Cache Settings: Global configuration, statistics display, clear cache functionality
- Model Pool Management: CRUD operations, auto-discovery feature, provider exclusion
- CLI Settings Management: Provider-based and Direct modes, full CRUD support
- Multi-Key Settings Modal: Manage API keys with rotation strategies and weights
- Manage Models Modal: View and manage models per provider (LLM and Embedding)
- Sync to CodexLens: Integration handler for provider configuration sync

Technical Implementation:
- Created 12 new React components in components/api-settings/
- Extended lib/api.ts with 460+ lines of API client functions
- Created hooks/useApiSettings.ts with 772 lines of TanStack Query hooks
- Added RadioGroup UI component for form selections
- Implemented unified error handling with useNotifications across all operations
- Complete i18n support (500+ keys in English and Chinese)
- Route integration (/api-settings) and sidebar navigation

Code Quality:
- All acceptance criteria from plan.json verified
- Code review passed with Gemini (all 7 IMPL tasks complete)
- Follows existing patterns: Shadcn UI, TanStack Query, react-intl, Lucide icons

ccw/frontend/src/locales/en/api-settings.json

@@ -128,7 +128,14 @@
     "modelBaseUrlHint": "Override base URL for this model",
     "basicInfo": "Basic Information",
     "endpointSettings": "Endpoint Settings",
-    "apiBaseUpdated": "Base URL updated"
+    "apiBaseUpdated": "Base URL updated",
+    "showDisabled": "Show Disabled",
+    "hideDisabled": "Hide Disabled",
+    "showAll": "Show All",
+    "saveError": "Failed to save provider",
+    "deleteError": "Failed to delete provider",
+    "toggleError": "Failed to toggle provider",
+    "testError": "Failed to test provider"
   },
   "endpoints": {
     "title": "Endpoints",
@@ -168,7 +175,13 @@
     "noEndpointsHint": "Add an endpoint to create custom API mappings with caching.",
     "providerBased": "Provider-based",
     "direct": "Direct",
-    "off": "Off"
+    "off": "Off",
+    "showDisabled": "Show Disabled",
+    "showAll": "Show All",
+    "basicInfo": "Basic Information",
+    "saveError": "Failed to save endpoint",
+    "deleteError": "Failed to delete endpoint",
+    "toggleError": "Failed to toggle endpoint"
   },
   "cache": {
     "title": "Cache",
@@ -249,6 +262,7 @@
   "cliSettings": {
     "title": "CLI Settings",
     "description": "Configure CLI tool settings and modes",
+    "modalDescription": "Configure Claude CLI wrapper settings for different endpoints",
     "stats": {
       "total": "Total Settings",
       "enabled": "Enabled"
@@ -263,12 +277,24 @@
       "title": "No CLI Settings Found",
       "message": "Add CLI settings to configure tool-specific options."
     },
+    "searchPlaceholder": "Search by name or description...",
     "mode": "Mode",
     "providerBased": "Provider-based",
     "direct": "Direct",
     "authToken": "Auth Token",
     "baseUrl": "Base URL",
-    "model": "Model"
+    "model": "Model",
+    "namePlaceholder": "e.g., production-claude",
+    "descriptionPlaceholder": "Optional description for this configuration",
+    "selectProvider": "Select a provider",
+    "includeCoAuthoredBy": "Include co-authored-by in commits",
+    "validation": {
+      "providerRequired": "Please select a provider",
+      "authOrBaseUrlRequired": "Please enter auth token or base URL"
+    },
+    "saveError": "Failed to save CLI settings",
+    "deleteError": "Failed to delete CLI settings",
+    "toggleError": "Failed to toggle CLI settings"
   },
   "ccwLitellm": {
     "title": "CCW-LiteLLM Package",
@@ -299,6 +325,7 @@
     "add": "Add",
     "close": "Close",
     "loading": "Loading...",
+    "saving": "Saving...",
     "error": "Error",
     "success": "Success",
     "warning": "Warning",
@@ -311,7 +338,12 @@
     "name": "Name",
     "description": "Description",
     "type": "Type",
-    "status": "Status"
+    "status": "Status",
+    "provider": "Provider",
+    "enableThis": "Enable this",
+    "validation": {
+      "nameRequired": "Name is required"
+    }
   },
   "messages": {
     "settingsSaved": "Settings saved successfully",

ccw/frontend/src/locales/en/codexlens.json

@@ -60,6 +60,26 @@
     "cancelled": "Cancelled",
     "inProgress": "In Progress"
   },
+  "semantic": {
+    "installTitle": "Install Semantic Search",
+    "installDescription": "Install FastEmbed and semantic search dependencies with GPU acceleration support.",
+    "installInfo": "GPU acceleration requires compatible hardware. CPU mode works on all systems but is slower.",
+    "gpu": {
+      "cpu": "CPU Mode",
+      "cpuDesc": "Universal compatibility, slower processing. Works on all systems.",
+      "directml": "DirectML (Windows GPU)",
+      "directmlDesc": "Best for Windows with AMD/Intel GPUs. Recommended for most users.",
+      "cuda": "CUDA (NVIDIA GPU)",
+      "cudaDesc": "Best performance with NVIDIA GPUs. Requires CUDA toolkit."
+    },
+    "recommended": "Recommended",
+    "install": "Install",
+    "installing": "Installing...",
+    "installSuccess": "Installation Complete",
+    "installSuccessDesc": "Semantic search installed successfully with {mode} mode",
+    "installFailed": "Installation Failed",
+    "unknownError": "An unknown error occurred"
+  },
   "settings": {
     "currentCount": "Current Index Count",
     "currentWorkers": "Current Workers",

ccw/frontend/src/locales/en/navigation.json

@@ -17,6 +17,7 @@
     "settings": "Settings",
     "mcp": "MCP Servers",
     "codexlens": "CodexLens",
+    "apiSettings": "API Settings",
     "endpoints": "CLI Endpoints",
     "installations": "Installations",
     "help": "Help",