backend: add push token API and FCM delivery pipeline

app/notifications/service.py

@@ -5,8 +5,18 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.chats.repository import is_chat_muted_for_user, list_chat_members
 from app.messages.models import Message
-from app.notifications.repository import create_notification_log, list_user_notifications
-from app.notifications.schemas import NotificationRead, NotificationRequest
+from app.notifications.repository import (
+    create_notification_log,
+    delete_push_device_token,
+    list_user_notifications,
+    upsert_push_device_token,
+)
+from app.notifications.schemas import (
+    NotificationRead,
+    NotificationRequest,
+    PushTokenDeleteRequest,
+    PushTokenUpsertRequest,
+)
 from app.notifications.tasks import send_mention_notification_task, send_push_notification_task
 from app.realtime.presence import is_user_online
 from app.users.repository import list_users_by_ids
@@ -98,3 +108,25 @@ async def get_notifications_for_user(db: AsyncSession, *, user_id: int, limit: i
     safe_limit = max(1, min(limit, 100))
     rows = await list_user_notifications(db, user_id=user_id, limit=safe_limit)
     return [NotificationRead.model_validate(item) for item in rows]
+
+
+async def register_push_token(db: AsyncSession, *, user_id: int, payload: PushTokenUpsertRequest) -> None:
+    await upsert_push_device_token(
+        db,
+        user_id=user_id,
+        platform=payload.platform.strip().lower(),
+        token=payload.token.strip(),
+        device_id=payload.device_id.strip() if payload.device_id else None,
+        app_version=payload.app_version.strip() if payload.app_version else None,
+    )
+    await db.commit()
+
+
+async def unregister_push_token(db: AsyncSession, *, user_id: int, payload: PushTokenDeleteRequest) -> None:
+    await delete_push_device_token(
+        db,
+        user_id=user_id,
+        platform=payload.platform.strip().lower(),
+        token=payload.token.strip(),
+    )
+    await db.commit()