feat: room search, room options sheet, .htaccess for E2EE

- Rooms screen: inline search filter with toggle — replaces the no-op button
- Chat screen: room options sheet — member list, invite, leave room
- rooms_repository: remove debug prints
- web/.htaccess: COOP+COEP headers for SharedArrayBuffer / LiveKit E2EE worker
  (was on production but missing from source; adds it to build output automatically)

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

pubspec.yaml

@@ -1,7 +1,7 @@
 name: m8chat_app
 description: "M8Chat — Matrix chat client for Android, iOS, and Web."
 publish_to: 'none'
-version: 1.3.0+4
+version: 1.3.1+5
 
 environment:
   sdk: '>=3.11.0 <4.0.0'