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_memory_backend.py

@@ -0,0 +1,42 @@
+"""Tests for InMemoryStateBackend."""
+
+from fusionagi.core.memory_backend import InMemoryStateBackend
+from fusionagi.schemas.task import Task, TaskState
+
+
+def test_set_and_get():
+    backend = InMemoryStateBackend()
+    task = Task(task_id="m1", goal="memory test")
+    backend.set_task(task)
+    assert backend.get_task("m1") is not None
+    assert backend.get_task("m1").goal == "memory test"
+
+
+def test_state_management():
+    backend = InMemoryStateBackend()
+    backend.set_task(Task(task_id="m2", goal="state"))
+    backend.set_task_state("m2", TaskState.ACTIVE)
+    assert backend.get_task_state("m2") == TaskState.ACTIVE
+
+
+def test_traces():
+    backend = InMemoryStateBackend()
+    backend.set_task(Task(task_id="m3", goal="traces"))
+    backend.append_trace("m3", {"a": 1})
+    backend.append_trace("m3", {"b": 2})
+    assert len(backend.get_trace("m3")) == 2
+
+
+def test_delete():
+    backend = InMemoryStateBackend()
+    backend.set_task(Task(task_id="m4", goal="del"))
+    assert backend.delete_task("m4") is True
+    assert backend.delete_task("m4") is False
+
+
+def test_list_and_count():
+    backend = InMemoryStateBackend()
+    for i in range(3):
+        backend.set_task(Task(task_id=f"l{i}", goal=f"g{i}"))
+    assert backend.count_tasks() == 3
+    assert len(backend.list_tasks()) == 3