refactor(core): distinguish network errors from auth failures and refactor real-time messaging pipeline

- Add isNetworkError() helper and FetchCurrentUserResult discriminated union to prevent logout on network failures
- Refactor authService to return { kind: 'user' } | { kind: 'auth_failed' } | { kind: 'network_error' }
- Update authStore to preserve login state on network errors, only logout on auth failures
- Replace WSMessageHandler with RealtimeIngestionPipeline for improved real-time message handling
- Remove MessageDeduplication service; add store-level idempotent addOrReplaceMessage for message dedup
- Add atomic systemUnreadCount operations to prevent race conditions
- Add SearchHeader component for consistent search UI across screens
- Add 'home' TabBar variant with underline style matching HomeScreen
- Add Jest test infrastructure and exclude tests from tsconfig
- Fix ChatScreen history lock being stuck when scrolling to latest messages
- Remove unused call_participant_joined/left WS event types

package.json

@@ -11,7 +11,9 @@
     "ios:simulator": "eas build --platform ios --profile ios-simulator",
     "ios:preview": "eas build --platform ios --profile preview",
     "ios:prod": "eas build --platform ios --profile production",
-    "ios:submit": "eas submit --platform ios --profile production"
+    "ios:submit": "eas submit --platform ios --profile production",
+    "test": "jest",
+    "test:watch": "jest --watch"
   },
   "dependencies": {
     "@expo/ui": "~56.0.17",
@@ -75,9 +77,12 @@
   },
   "devDependencies": {
     "@react-native-community/cli": "^20.1.3",
+    "@types/jest": "^29.5.12",
     "@types/pako": "^2.0.4",
     "@types/react": "~19.2.16",
     "@types/react-native-vector-icons": "^6.4.18",
+    "jest": "^29.7.0",
+    "ts-jest": "^29.1.2",
     "typescript": "~6.0.3"
   },
   "private": true,