Wire all integrations + production hardening: 15 recommendations

Integration & Wiring:
- useStore/useAppState wired into App.tsx (replaces 8 useState calls)
- React Router wired at app root (URL-based navigation)
- SparklineChart/MetricCard/BarChart integrated into Admin + Ethics pages
- useNotifications.handleWSEvent wired into WebSocket handler
- Notification center dropdown in header with unread badge
- Locale selector added to Settings page (6 languages)
- Dashboard data fetching with 10s polling into MetricCards
- File drag-and-drop support on chat area

Production Hardening:
- PostgresStateBackend with connection pooling (psycopg2)
- App lifespan wires backend from FUSIONAGI_DB_BACKEND env (memory|sqlite|postgres)
- Redis cache wired from FUSIONAGI_REDIS_URL env at startup
- Multi-process uvicorn config for horizontal scaling

Testing:
- Playwright visual regression tests (12 stories x 2 viewports)
- k6 load test script with ramp/spike/ramp-down stages
- 7 new Python tests (postgres fallback, app wiring)

575 Python tests + 45 frontend tests = 620 total, 0 ruff errors.

Co-Authored-By: Nakamoto, S <defi@defi-oracle.io>

tests/test_app_wiring.py

@@ -0,0 +1,34 @@
+"""Tests for app lifespan backend/cache wiring."""
+
+
+from fusionagi.api.app import create_app
+
+
+def test_create_app_default():
+    """App should create successfully with default (memory) backend."""
+    app = create_app()
+    assert app is not None
+    assert app.title == "FusionAGI Dvādaśa API"
+
+
+def test_create_app_with_sqlite_env(tmp_path, monkeypatch):
+    """App should accept FUSIONAGI_DB_BACKEND=sqlite env."""
+    monkeypatch.setenv("FUSIONAGI_DB_BACKEND", "sqlite")
+    monkeypatch.setenv("FUSIONAGI_SQLITE_PATH", str(tmp_path / "test.db"))
+    app = create_app()
+    assert app is not None
+
+
+def test_create_app_with_invalid_postgres(monkeypatch):
+    """App should gracefully fall back when Postgres DSN is invalid."""
+    monkeypatch.setenv("FUSIONAGI_DB_BACKEND", "postgres")
+    monkeypatch.setenv("FUSIONAGI_POSTGRES_DSN", "postgresql://invalid:invalid@localhost:1/invalid")
+    app = create_app()
+    assert app is not None
+
+
+def test_create_app_with_invalid_redis(monkeypatch):
+    """App should gracefully fall back when Redis URL is invalid."""
+    monkeypatch.setenv("FUSIONAGI_REDIS_URL", "redis://localhost:1/0")
+    app = create_app()
+    assert app is not None