feat: Integrate Electric SQL for real-time notifications and enhance PostgreSQL configuration

- Added Electric SQL service to docker-compose for real-time data synchronization.
- Introduced PostgreSQL configuration for logical replication and performance tuning.
- Created scripts for initializing Electric SQL user and electrifying tables.
- Implemented notification model and service in the backend.
- Developed ElectricProvider and useNotifications hook in the frontend for managing notifications.
- Updated environment variables and package dependencies for Electric SQL integration.

surfsense_backend/app/db.py

@@ -492,6 +492,12 @@ class SearchSpace(BaseModel, TimestampMixin):
         order_by="Log.id",
         cascade="all, delete-orphan",
     )
+    notifications = relationship(
+        "Notification",
+        back_populates="search_space",
+        order_by="Notification.created_at.desc()",
+        cascade="all, delete-orphan",
+    )
     search_source_connectors = relationship(
         "SearchSourceConnector",
         back_populates="search_space",
@@ -629,6 +635,25 @@ class Log(BaseModel, TimestampMixin):
     search_space = relationship("SearchSpace", back_populates="logs")
 
 
+class Notification(BaseModel, TimestampMixin):
+    __tablename__ = "notifications"
+
+    user_id = Column(
+        UUID(as_uuid=True), ForeignKey("user.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    search_space_id = Column(
+        Integer, ForeignKey("searchspaces.id", ondelete="CASCADE"), nullable=True
+    )
+    type = Column(String(50), nullable=False)  # 'document_processed', 'connector_indexed', 'user_mentioned', etc.
+    title = Column(String(200), nullable=False)
+    message = Column(Text, nullable=False)
+    read = Column(Boolean, nullable=False, default=False, server_default=text("false"), index=True)
+    notification_metadata = Column("metadata", JSONB, nullable=True, default={})
+
+    user = relationship("User", back_populates="notifications")
+    search_space = relationship("SearchSpace", back_populates="notifications")
+
+
 class SearchSpaceRole(BaseModel, TimestampMixin):
     """
     Custom roles that can be defined per search space.
@@ -773,6 +798,12 @@ if config.AUTH_TYPE == "GOOGLE":
             "OAuthAccount", lazy="joined"
         )
         search_spaces = relationship("SearchSpace", back_populates="user")
+        notifications = relationship(
+            "Notification",
+            back_populates="user",
+            order_by="Notification.created_at.desc()",
+            cascade="all, delete-orphan",
+        )
 
         # RBAC relationships
         search_space_memberships = relationship(
@@ -799,6 +830,12 @@ else:
 
     class User(SQLAlchemyBaseUserTableUUID, Base):
         search_spaces = relationship("SearchSpace", back_populates="user")
+        notifications = relationship(
+            "Notification",
+            back_populates="user",
+            order_by="Notification.created_at.desc()",
+            cascade="all, delete-orphan",
+        )
 
         # RBAC relationships
         search_space_memberships = relationship(