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>

fusionagi/core/memory_backend.py

@@ -0,0 +1,68 @@
+"""In-memory state backend for task persistence.
+
+Useful for testing and development when no database is needed.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from fusionagi.core.persistence import StateBackend
+from fusionagi.schemas.task import Task, TaskState
+
+
+class InMemoryStateBackend(StateBackend):
+    """In-memory implementation of StateBackend.
+
+    All data is lost on process restart. Use SQLiteStateBackend
+    or a Postgres-backed backend for production persistence.
+    """
+
+    def __init__(self) -> None:
+        self._tasks: dict[str, Task] = {}
+        self._traces: dict[str, list[dict[str, Any]]] = {}
+
+    def get_task(self, task_id: str) -> Task | None:
+        """Load task by id."""
+        return self._tasks.get(task_id)
+
+    def set_task(self, task: Task) -> None:
+        """Save task."""
+        self._tasks[task.task_id] = task
+
+    def get_task_state(self, task_id: str) -> TaskState | None:
+        """Return current task state or None if task unknown."""
+        task = self._tasks.get(task_id)
+        return task.state if task else None
+
+    def set_task_state(self, task_id: str, state: TaskState) -> None:
+        """Update task state; creates no task if missing."""
+        task = self._tasks.get(task_id)
+        if task is not None:
+            self._tasks[task_id] = task.model_copy(update={"state": state})
+
+    def append_trace(self, task_id: str, entry: dict[str, Any]) -> None:
+        """Append trace entry."""
+        if task_id not in self._traces:
+            self._traces[task_id] = []
+        self._traces[task_id].append(entry)
+
+    def get_trace(self, task_id: str) -> list[dict[str, Any]]:
+        """Load trace for task."""
+        return list(self._traces.get(task_id, []))
+
+    def list_tasks(self, state: TaskState | None = None, limit: int = 100) -> list[Task]:
+        """List tasks, optionally filtered by state."""
+        tasks = list(self._tasks.values())
+        if state is not None:
+            tasks = [t for t in tasks if t.state == state]
+        return tasks[:limit]
+
+    def delete_task(self, task_id: str) -> bool:
+        """Delete a task and its traces."""
+        self._traces.pop(task_id, None)
+        return self._tasks.pop(task_id, None) is not None
+
+    def count_tasks(self) -> int:
+        """Return total task count."""
+        return len(self._tasks)