feat(proxy): implement provider adapter pattern with OpenRouter support

This major refactoring introduces a modular provider adapter architecture
to support format transformation between different AI API formats.

New features:
- Add ProviderAdapter trait for unified provider abstraction
- Implement Claude, Codex, and Gemini adapters with specific logic
- Add Anthropic ↔ OpenAI format transformation for OpenRouter compatibility
- Support model mapping from provider configuration (ANTHROPIC_MODEL, etc.)
- Add OpenRouter preset to Claude provider presets

Refactoring:
- Extract authentication logic into auth.rs with AuthInfo and AuthStrategy
- Move URL building and request transformation to individual adapters
- Simplify ProviderRouter to only use proxy target providers
- Refactor RequestForwarder to use adapter-based request/response handling
- Use whitelist mode for header forwarding (only pass necessary headers)

Architecture:
- providers/adapter.rs: ProviderAdapter trait definition
- providers/auth.rs: AuthInfo, AuthStrategy types
- providers/claude.rs: Claude adapter with OpenRouter detection
- providers/codex.rs: Codex (OpenAI) adapter
- providers/gemini.rs: Gemini (Google) adapter
- providers/models/: Anthropic and OpenAI API data models
- providers/transform.rs: Bidirectional format transformation

src/App.tsx

@@ -315,13 +315,14 @@ function App() {
                   isLoading={isLoading}
                   onSwitch={switchProvider}
                   onSetProxyTarget={setProxyTarget}
-              onEdit={setEditingProvider}
-              onDelete={setConfirmDelete}
-              onDuplicate={handleDuplicateProvider}
-              onConfigureUsage={setUsageProvider}
-              onOpenWebsite={handleOpenWebsite}
-              onCreate={() => setIsAddOpen(true)}
-            /></div>
+                  onEdit={setEditingProvider}
+                  onDelete={setConfirmDelete}
+                  onDuplicate={handleDuplicateProvider}
+                  onConfigureUsage={setUsageProvider}
+                  onOpenWebsite={handleOpenWebsite}
+                  onCreate={() => setIsAddOpen(true)}
+                />
+              </div>
             </div>
           </div>
         );

src/config/claudeProviderPresets.ts

@@ -365,4 +365,22 @@ export const providerPresets: ProviderPreset[] = [
     partnerPromotionKey: "packycode", // 促销信息 i18n key
     icon: "packycode",
   },
+  {
+    name: "OpenRouter",
+    websiteUrl: "https://openrouter.ai",
+    apiKeyUrl: "https://openrouter.ai/keys",
+    settingsConfig: {
+      env: {
+        ANTHROPIC_BASE_URL: "https://openrouter.ai/api",
+        ANTHROPIC_AUTH_TOKEN: "",
+        ANTHROPIC_MODEL: "anthropic/claude-sonnet-4.5",
+        ANTHROPIC_DEFAULT_HAIKU_MODEL: "anthropic/claude-haiku-4.5",
+        ANTHROPIC_DEFAULT_SONNET_MODEL: "anthropic/claude-sonnet-4.5",
+        ANTHROPIC_DEFAULT_OPUS_MODEL: "anthropic/claude-opus-4.5",
+      },
+    },
+    category: "aggregator",
+    icon: "openrouter",
+    iconColor: "#6366F1",
+  },
 ];