feat: Google Photos provider backend + API hardening

- Add Google Photos provider: client, models, change detector, capabilities
- Add notification templates (en/ru) for all GP event slots
- Add command templates (en/ru) for GP bot commands
- Register GP in slot/command loaders, capabilities, and seeds
- Harden provider API: validate OAuth credentials on create/update
- Add internal URL rewriting for asset fetches (LAN optimization)
- Fix template renderer to handle missing variables gracefully
- Improve webhook command routing for multi-provider support
- Add provider health check endpoint and watcher improvements

packages/server/src/notify_bridge_server/api/webhooks.py

@@ -156,7 +156,6 @@ async def gitea_webhook(provider_id: int, request: Request):
                     )},
                 },
             ))
-            await session.commit()
 
             # Dispatch to targets
             dispatcher = NotificationDispatcher()
@@ -172,6 +171,8 @@ async def gitea_webhook(provider_id: int, request: Request):
                             tracker.id, r.get("error", "unknown"),
                         )
 
+        await session.commit()
+
     return {"ok": True, "dispatched": dispatched}
 
 
@@ -268,7 +269,6 @@ async def planka_webhook(provider_id: int, request: Request):
                     )},
                 },
             ))
-            await session.commit()
 
             # Dispatch to targets
             dispatcher = NotificationDispatcher()
@@ -284,6 +284,8 @@ async def planka_webhook(provider_id: int, request: Request):
                             tracker.id, r.get("error", "unknown"),
                         )
 
+        await session.commit()
+
     return {"ok": True, "dispatched": dispatched}