Add push notification functionality with tests and digest scheduler

- Implemented push subscription API with tests for subscribing and unsubscribing users.
- Created web push notification tests triggered by child actions.
- Added digest scheduler to send email digests to users at 9 PM local time.
- Developed utility functions for creating and validating digest action tokens.
- Integrated web push sender to handle sending notifications to users.
- Added service worker for handling push notifications in the frontend.
- Created a push opt-in component for user notification preferences.
- Implemented tests for the push opt-in component to ensure correct behavior.
- Updated frontend services to manage push subscriptions and permissions.

backend/db/digest_action_tokens.py

@@ -0,0 +1,18 @@
+from tinydb import Query
+from db.db import digest_action_tokens_db
+from models.digest_action_token import DigestActionToken
+
+
+def insert_token(token: DigestActionToken) -> None:
+    digest_action_tokens_db.insert(token.to_dict())
+
+
+def get_token_by_id(token_id: str) -> DigestActionToken | None:
+    Q = Query()
+    result = digest_action_tokens_db.get(Q.id == token_id)
+    return DigestActionToken.from_dict(result) if result else None
+
+
+def mark_token_used(token_id: str) -> None:
+    Q = Query()
+    digest_action_tokens_db.update({'used': True}, Q.id == token_id)