Restructure chat service, web routes, and add test suite

Split monolithic chat service into modular structure with Matrix client
support, extract web server into per-resource route modules, introduce
bootstrap/main-loop separation, and add comprehensive vitest coverage
across services, repositories, and utilities. Adds project docs and
CLAUDE.md agent instructions.

src/services/media.ts

@@ -57,9 +57,10 @@ export class MediaService {
 
   constructor(
     private downloader: MediaDownloader,
-    private logger: Logger
+    private logger: Logger,
+    mediaRoot?: string,
   ) {
-    this.mediaRoot = path.join(process.cwd(), 'data', 'media');
+    this.mediaRoot = mediaRoot ?? path.join(process.cwd(), 'data', 'media');
     this.indexPath = path.join(this.mediaRoot, 'index.json');
   }
 
@@ -84,7 +85,7 @@ export class MediaService {
 
   async getMediaItems(): Promise<MediaRecord[]> {
     await this.loadIndex();
-    return (this.index?.items || []).slice().sort((a, b) => b.createdAt - a.createdAt);
+    return (this.index?.items || []).slice().sort((a, b) => b.timestamp - a.timestamp);
   }
 
   private async downloadMessageMedia(chat: ActiveChat, message: ScrapedChatMessage): Promise<ChatMedia[]> {