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/schemas/audit_log.py

@@ -0,0 +1,65 @@
+"""Pydantic schemas for Audit Log API requests/responses."""
+
+from datetime import datetime
+from typing import Optional, List, Any
+from pydantic import BaseModel, Field
+
+
+class AuditLogBase(BaseModel):
+    """Base audit log schema."""
+    action: str = Field(..., max_length=50)
+    resource_type: Optional[str] = Field(None, max_length=50)
+    resource_id: Optional[str] = Field(None, max_length=255)
+    details: Optional[str] = None
+    ip_address: Optional[str] = Field(None, max_length=45)
+    user_agent: Optional[str] = Field(None, max_length=500)
+    status: str = Field(default="success", max_length=20)
+
+
+class AuditLogCreate(AuditLogBase):
+    """Schema for creating an audit log entry."""
+    user_id: Optional[str] = None
+    username: Optional[str] = None
+
+
+class AuditLog(AuditLogBase):
+    """Schema for audit log response."""
+    id: str
+    user_id: Optional[str] = None
+    username: Optional[str] = None
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class AuditLogList(BaseModel):
+    """Schema for paginated audit log list."""
+    items: List[AuditLog]
+    total: int
+    page: int
+    page_size: int
+    total_pages: int
+
+
+class AuditLogFilter(BaseModel):
+    """Schema for filtering audit logs."""
+    user_id: Optional[str] = None
+    username: Optional[str] = None
+    action: Optional[str] = None
+    resource_type: Optional[str] = None
+    resource_id: Optional[str] = None
+    status: Optional[str] = None
+    start_date: Optional[datetime] = None
+    end_date: Optional[datetime] = None
+
+
+class AuditLogStats(BaseModel):
+    """Schema for audit log statistics."""
+    total_entries: int
+    entries_today: int
+    entries_this_week: int
+    entries_this_month: int
+    actions_breakdown: dict[str, int]
+    top_users: List[dict[str, Any]]
+    recent_failures: int