Phase 2 refinements: Firebase config, dev environment fixes, phase 3 requirement draft

- Integrated Firebase SDK in both Flutter apps (google-services, firebase_options)
- Fixed auth flow, API client, and pairing/status blocs for dev environment
- Added full Flutter project scaffolds (android, ios, web, etc.)
- Added phase 3 chat engine requirement document
- Added bugreport zip pattern to gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/server.js

@@ -2,12 +2,14 @@ import 'dotenv/config'
 import { buildPublicApp } from './app.public.js'
 import { buildInternalApp } from './app.internal.js'
 import { autoOfflineStaleMitras } from './services/mitra-status.service.js'
+import { initFirebase } from './plugins/firebase.js'
 
 const PUBLIC_PORT = process.env.PUBLIC_PORT || 3000
 const INTERNAL_PORT = process.env.INTERNAL_PORT || 3001
 const INTERNAL_HOST = process.env.INTERNAL_HOST || '127.0.0.1'
 
 const start = async () => {
+  initFirebase()
   const publicApp = await buildPublicApp()
   const internalApp = await buildInternalApp()