Add comprehensive backend features and mobile UI improvements

Backend:
- Add 2FA authentication with TOTP support
- Add API keys management system
- Add audit logging for security events
- Add file upload/management system
- Add notifications system with preferences
- Add session management
- Add webhooks integration
- Add analytics endpoints
- Add export functionality
- Add password policy enforcement
- Add new database migrations for core tables

Frontend:
- Add module position system (top/bottom sidebar sections)
- Add search and notifications module configuration tabs
- Add mobile logo replacing hamburger menu
- Center page title absolutely when no tabs present
- Align sidebar footer toggles with navigation items
- Add lighter icon color in dark theme for mobile
- Add API keys management page
- Add notifications page with context
- Add admin analytics and audit logs pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/models/notification.py

@@ -0,0 +1,51 @@
+"""Notification database model for in-app notifications."""
+
+import json
+import uuid
+from sqlalchemy import Column, String, Boolean, ForeignKey, Text
+from sqlalchemy.sql import func
+from sqlalchemy.types import DateTime
+
+from app.db.base import Base
+
+
+class Notification(Base):
+    """Notification model for in-app user notifications."""
+
+    __tablename__ = "notifications"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+
+    # Recipient
+    user_id = Column(String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+
+    # Notification content
+    title = Column(String(200), nullable=False)
+    message = Column(Text, nullable=True)
+    type = Column(String(50), default="info")  # info, success, warning, error, system
+
+    # Link (optional) - where to navigate when clicked
+    link = Column(String(500), nullable=True)
+
+    # Extra data (JSON string)
+    extra_data = Column(Text, nullable=True)
+
+    # Status
+    is_read = Column(Boolean, default=False, nullable=False, index=True)
+
+    # Timestamps
+    created_at = Column(DateTime, server_default=func.now(), nullable=False, index=True)
+    read_at = Column(DateTime, nullable=True)
+
+    @property
+    def parsed_extra_data(self) -> dict | None:
+        """Get extra_data as parsed dict."""
+        if self.extra_data:
+            try:
+                return json.loads(self.extra_data)
+            except json.JSONDecodeError:
+                return None
+        return None
+
+    def __repr__(self):
+        return f"<Notification(id={self.id}, user_id={self.user_id}, title='{self.title[:30]}')>"