feat(aigc): implement travel AIGC feature and clean up legacy assets

- Replace all local static AIGC assets with OSS hosted URLs to reduce bundle size
- Add travelAIGC command to ChatModel and update quick access menu to link to AIGC home
- Implement AIGC user consent flow with local storage persistence for compliance
- Refactor Discovery page layout, remove unused HeritageDiscoverySection component
- Update ChatTopNavBar to support dynamic navigation bar height based on system info
- Restructure ChatMainList layout for better discovery panel interaction
- Remove deprecated local asset files and clean up unused imports across codebase

src/model/ChatModel.js

@@ -99,4 +99,6 @@ export const Command = {
   feedbackCard: "Command.feedbackCard",
   // 生成合成图片
   aigcPhotoGenerator: "Command.aigcPhotoGenerator",
+  // 旅行AIGC
+  travelAIGC: "Command.travelAIGC",
 };