Add DB+.env auto backup with download and upload restore in Settings.

Backups land under /root/eth_hedge_backups; restore accepts zip body for new-server migration and restarts the process.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/main.py

@@ -59,6 +59,10 @@ async def lifespan(app: FastAPI):
             logger.exception("LIVE startup reconcile log failed")
     engine.ensure_loop()
 
+    from .backup import start_auto_backup_task
+
+    start_auto_backup_task()
+
     session = bootstrap_session(settings)
     try:
         await session.start()
@@ -79,6 +83,9 @@ async def lifespan(app: FastAPI):
             await engine._task
         except Exception:
             pass
+    from .backup import stop_auto_backup_task
+
+    await stop_auto_backup_task()
     await session.stop()
     from .exchange import set_exchange
     from .strategy.session import set_session