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/session.py

@@ -0,0 +1,46 @@
+"""User session database model for tracking active sessions."""
+
+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 UserSession(Base):
+    """User session model for tracking active sessions."""
+
+    __tablename__ = "user_sessions"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+
+    # User
+    user_id = Column(String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+
+    # Token hash (to identify and revoke specific sessions)
+    token_hash = Column(String(64), unique=True, nullable=False, index=True)
+
+    # Device/client info
+    device_name = Column(String(200), nullable=True)  # User-friendly name
+    device_type = Column(String(50), nullable=True)  # desktop, mobile, tablet
+    browser = Column(String(100), nullable=True)
+    os = Column(String(100), nullable=True)
+    user_agent = Column(String(500), nullable=True)
+
+    # Location info
+    ip_address = Column(String(45), nullable=True)
+    location = Column(String(200), nullable=True)  # City, Country
+
+    # Status
+    is_active = Column(Boolean, default=True, nullable=False)
+    is_current = Column(Boolean, default=False, nullable=False)  # Marks the current session
+
+    # Timestamps
+    created_at = Column(DateTime, server_default=func.now(), nullable=False, index=True)
+    last_active_at = Column(DateTime, server_default=func.now(), nullable=False)
+    expires_at = Column(DateTime, nullable=True)
+    revoked_at = Column(DateTime, nullable=True)
+
+    def __repr__(self):
+        return f"<UserSession(id={self.id}, user_id={self.user_id}, device={self.device_name})>"