feat: add Ampcode (Amp CLI Integration) support with configuration UI and i18n

- Add ampcodeApi service for upstream URL, API key, and model mappings management
  - Implement Ampcode configuration modal in AiProvidersPage
  - Add complete i18n translations for Ampcode features (en and zh-CN)
  - Enhance UsagePage with mobile-responsive chart improvements and legend display
  - Optimize chart rendering for smaller screens
  - Improve page layout styles (SystemPage, AiProvidersPage alignment)

src/stores/useConfigStore.ts

@@ -37,6 +37,7 @@ const SECTION_KEYS: RawConfigSection[] = [
   'logging-to-file',
   'ws-auth',
   'api-keys',
+  'ampcode',
   'gemini-api-key',
   'codex-api-key',
   'claude-api-key',
@@ -65,6 +66,8 @@ const extractSectionValue = (config: Config | null, section?: RawConfigSection)
       return config.wsAuth;
     case 'api-keys':
       return config.apiKeys;
+    case 'ampcode':
+      return config.ampcode;
     case 'gemini-api-key':
       return config.geminiApiKeys;
     case 'codex-api-key':
@@ -166,6 +169,9 @@ export const useConfigStore = create<ConfigState>((set, get) => ({
         case 'api-keys':
           nextConfig.apiKeys = value;
           break;
+        case 'ampcode':
+          nextConfig.ampcode = value;
+          break;
         case 'gemini-api-key':
           nextConfig.geminiApiKeys = value;
           break;