feat: Add notifications table and integrate Electric SQL for real-time updates

- Introduced a new notifications table in the database schema to manage user notifications.
- Implemented Electric SQL replication setup for the notifications table, ensuring real-time synchronization.
- Updated existing database functions to support real-time updates for connectors and documents using Electric SQL.
- Refactored UI components to utilize new hooks for fetching connectors and documents, enhancing performance and user experience.

surfsense_backend/alembic/versions/61_add_notifications_table.py

@@ -0,0 +1,53 @@
+"""Add notifications table
+
+Revision ID: 61
+Revises: 60
+
+Note: Electric SQL replication setup (REPLICA IDENTITY FULL and publication)
+is handled in app/db.py setup_electric_replication() which runs on app startup.
+"""
+from collections.abc import Sequence
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "61"
+down_revision: str | None = "60"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Upgrade schema - add notifications table."""
+    # Create notifications table
+    op.execute(
+        """
+        CREATE TABLE IF NOT EXISTS notifications (
+            id SERIAL PRIMARY KEY,
+            user_id UUID NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+            search_space_id INTEGER REFERENCES searchspaces(id) ON DELETE CASCADE,
+            type VARCHAR(50) NOT NULL,
+            title VARCHAR(200) NOT NULL,
+            message TEXT NOT NULL,
+            read BOOLEAN NOT NULL DEFAULT FALSE,
+            metadata JSONB DEFAULT '{}',
+            created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+            updated_at TIMESTAMPTZ
+        );
+        """
+    )
+
+    # Create indexes
+    op.create_index("ix_notifications_user_id", "notifications", ["user_id"])
+    op.create_index("ix_notifications_read", "notifications", ["read"])
+    op.create_index("ix_notifications_created_at", "notifications", ["created_at"])
+    op.create_index("ix_notifications_user_read", "notifications", ["user_id", "read"])
+
+
+def downgrade() -> None:
+    """Downgrade schema - remove notifications table."""
+    op.drop_index("ix_notifications_user_read", table_name="notifications")
+    op.drop_index("ix_notifications_created_at", table_name="notifications")
+    op.drop_index("ix_notifications_read", table_name="notifications")
+    op.drop_index("ix_notifications_user_id", table_name="notifications")
+    op.drop_table("notifications")