Phase 3 testing fixes: Fastify 5, SSE→WebSocket+FCM, enums, security, session lifecycle

- Upgrade Fastify 4→5 with all plugins (@fastify/websocket 11, cors 11, sensible 6)
- Migrate all SSE endpoints to WebSocket + FCM push (mitra chat requests, customer pairing status)
- Add flutter_local_notifications for foreground push notifications with sound
- Add splash screen to both apps (hide auth loading flash)
- Introduce constants/enums across entire codebase (no raw string literals)
- Move price tiers from hardcoded array to app_config DB (data-driven, includes 1-min test tier)
- Add session ownership validation on all shared chat routes
- Add ownership checks on endSession, respondToExtension, requestExtension
- Fix session timer: auto-complete expired/stale sessions on server restart
- Add 5-min grace period for abandoned closing sessions
- Fix extension flow: proper session_resumed handling, clearExtensionRequest, closure grace timer cleanup
- Fix chat screens: ConnectChat in initState, session status check on connect
- Fix customer expired view: 5-min countdown, closure state priority over expired state
- Fix mitra extension UI: loading spinner, disable buttons, handle EXTENSION_RESOLVED error
- Fix GoRouter navigation consistency (no more Navigator.pushNamed)
- Fix goodbye view keyboard overflow (SingleChildScrollView)
- Add active session card on customer home screen with refresh on navigate back
- Fix PricingBottomSheet extension mode (RequestExtension instead of new pairing)
- Send session_resumed to both parties on extension accept

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

client_app/pubspec.lock

@@ -9,6 +9,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.3.35"
+  args:
+    dependency: transitive
+    description:
+      name: args
+      sha256: d0481093c50b1da8910eb0bb301626d4d8eb7284aa739614d2b394ee09e3ea04
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.7.0"
   async:
     dependency: transitive
     description:
@@ -65,6 +73,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.7"
+  dbus:
+    dependency: transitive
+    description:
+      name: dbus
+      sha256: d0c98dcd4f5169878b6cf8f6e0a52403a9dff371a3e2f019697accbf6f44a270
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.7.12"
   dio:
     dependency: "direct main"
     description:
@@ -206,6 +222,38 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.2"
+  flutter_local_notifications:
+    dependency: "direct main"
+    description:
+      name: flutter_local_notifications
+      sha256: "0d9035862236fe38250fe1644d7ed3b8254e34a21b2c837c9f539fbb3bba5ef1"
+      url: "https://pub.dev"
+    source: hosted
+    version: "21.0.0"
+  flutter_local_notifications_linux:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_linux
+      sha256: e0f25e243c6c44c825bbbc6b2b2e76f7d9222362adcfe9fd780bf01923c840bd
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.0.0"
+  flutter_local_notifications_platform_interface:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_platform_interface
+      sha256: e7db3d5b49c2b7ecc68deba4aaaa67a348f92ee0fef34c8e4b4459dbef0d7307
+      url: "https://pub.dev"
+    source: hosted
+    version: "11.0.0"
+  flutter_local_notifications_windows:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_windows
+      sha256: "3a2654ba104fbb52c618ebed9def24ef270228470718c43b3a6afcd5c81bef0c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.0"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -400,6 +448,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.3.0"
+  petitparser:
+    dependency: transitive
+    description:
+      name: petitparser
+      sha256: "91bd59303e9f769f108f8df05e371341b15d59e995e6806aefab827b58336675"
+      url: "https://pub.dev"
+    source: hosted
+    version: "7.0.2"
   platform:
     dependency: transitive
     description:
@@ -557,6 +613,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.7.7"
+  timezone:
+    dependency: transitive
+    description:
+      name: timezone
+      sha256: "784a5e34d2eb62e1326f24d6f600aaaee452eb8ca8ef2f384a59244e292d158b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.11.0"
   typed_data:
     dependency: transitive
     description:
@@ -605,6 +669,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.0"
+  xml:
+    dependency: transitive
+    description:
+      name: xml
+      sha256: "971043b3a0d3da28727e40ed3e0b5d18b742fa5a68665cca88e74b7876d5e025"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.6.1"
 sdks:
-  dart: ">=3.9.0 <4.0.0"
-  flutter: ">=3.35.0"
+  dart: ">=3.10.0 <4.0.0"
+  flutter: ">=3.38.1"