Next-level improvements: 15 items across backend, frontend, and testing

Backend:
- SQLiteStateBackend: persistent task/trace storage with SQLite
- InMemoryStateBackend: in-memory impl of StateBackend interface
- Redis cache backend (CacheBackend ABC + MemoryCacheBackend + RedisCacheBackend)
- OpenAI adapter: async acomplete() with retry logic
- Per-tenant + per-IP rate limiting in middleware

Frontend:
- State management: useStore + useAppState (zero-dep, context + reducer)
- React Router integration: URL-based navigation (usePageNavigation)
- WebSocket streaming: sendPrompt + StreamCallbacks for token-by-token updates
- File preview: inline image/text/binary preview with expand/collapse
- Sparkline charts + MetricCard + BarChart for dashboard visualization
- Push notifications hook (useNotifications) with browser Notification API
- i18n system: 6 locales (en, es, fr, de, ja, zh) with interpolation
- 6 new Storybook stories (ChatMessage, Skeleton, Markdown, SearchFilter, Toast, FilePreview)

Testing:
- Playwright E2E config + 6 browser specs (desktop + mobile)
- 18 new Python tests (SQLiteStateBackend, InMemoryStateBackend, cache backends)

570 Python tests + 45 frontend tests = 615 total, 0 ruff errors.

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

tests/test_cache_backends.py

@@ -0,0 +1,48 @@
+"""Tests for ResponseCache with pluggable backends."""
+
+from fusionagi.api.cache import MemoryCacheBackend, ResponseCache
+
+
+def test_memory_backend_basic():
+    backend = MemoryCacheBackend(max_size=10, default_ttl=60.0)
+    backend.set("k1", {"data": "value"})
+    assert backend.get("k1") == {"data": "value"}
+
+
+def test_memory_backend_delete():
+    backend = MemoryCacheBackend()
+    backend.set("k2", "val")
+    assert backend.delete("k2") is True
+    assert backend.get("k2") is None
+
+
+def test_memory_backend_clear():
+    backend = MemoryCacheBackend()
+    backend.set("a", 1)
+    backend.set("b", 2)
+    assert backend.clear() == 2
+    assert backend.get("a") is None
+
+
+def test_memory_backend_stats():
+    backend = MemoryCacheBackend(max_size=100)
+    backend.set("s1", "v1")
+    stats = backend.stats()
+    assert stats["backend"] == "memory"
+    assert stats["total"] == 1
+
+
+def test_response_cache_with_backend():
+    backend = MemoryCacheBackend(max_size=50, default_ttl=120.0)
+    cache = ResponseCache(backend=backend)
+    cache.set("hello", "session-1", {"answer": "world"})
+    assert cache.get("hello", "session-1") == {"answer": "world"}
+    assert cache.get("hello", "session-2") is None  # different session
+
+
+def test_response_cache_tenant_isolation():
+    cache = ResponseCache()
+    cache.set("prompt", "s1", "result-a", tenant_id="tenant-1")
+    cache.set("prompt", "s1", "result-b", tenant_id="tenant-2")
+    assert cache.get("prompt", "s1", "tenant-1") == "result-a"
+    assert cache.get("prompt", "s1", "tenant-2") == "result-b"