fix(desktop): component cleanup + dead code removal + DeerFlow ai-elements

- ChatArea: DeerFlow ai-elements annotations for accessibility
- Conversation: remove unused Context, simplify message rendering
- Delete dead modules: audit-logger.ts, gateway-reconnect.ts
- Replace console.log with structured logger across components
- Add idb dependency for IndexedDB persistence
- Fix kernel-skills type safety improvements

desktop/src/components/ai/index.ts

@@ -1,4 +1,4 @@
-export { Conversation, ConversationProvider, useConversationContext } from './Conversation';
+export { Conversation } from './Conversation';
 export { ReasoningBlock } from './ReasoningBlock';
 export { StreamingText } from './StreamingText';
 export { ChatMode, type ChatModeType, type ChatModeConfig, CHAT_MODES } from './ChatMode';