feat(#383): Streaming AI responses via Matrix message edits

- Add MatrixStreamingService with editMessage, setTypingIndicator, streamResponse
- Rate-limited edits (500ms) for incremental streaming output
- Typing indicator management during generation
- Graceful error handling and fallback for non-streaming scenarios
- Add optional editMessage to IChatProvider interface
- Add getClient() accessor to MatrixService for streaming service
- Register MatrixStreamingService in BridgeModule
- Tests: 20 tests pass

Refs #383

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/bridge/matrix/index.ts

@@ -1,2 +1,4 @@
 export { MatrixService } from "./matrix.service";
 export { MatrixRoomService } from "./matrix-room.service";
+export { MatrixStreamingService } from "./matrix-streaming.service";
+export type { StreamResponseOptions } from "./matrix-streaming.service";