Phase 2 Step 5: Implement Basic UI Templates

Implement comprehensive web UI with dark slate theme matching HTML reports:

Templates:
- Create base.html with navigation, dark theme (#0f172a background)
- Update dashboard.html with stats cards and recent scans table
- Update scans.html with pagination, filtering, and status badges
- Update scan_detail.html with comprehensive scan results display
- Update login.html to extend base template with centered design

Features:
- AJAX-powered dynamic data loading from API endpoints
- Auto-refresh for running scans (10-15 second intervals)
- Responsive Bootstrap 5 grid layout
- Color scheme matches report_mockup.html (slate dark theme)
- Status badges (success/danger/warning/info) with proper colors
- Modal dialogs for triggering scans
- Pagination with ellipsis for large result sets
- Delete confirmation dialogs
- Loading spinners for async operations

Bug Fixes:
- Fix scanner.py imports to use 'src.' prefix for module imports
- Fix scans.py to import validate_page_params from pagination module

All templates use consistent color palette:
- Background: #0f172a, Cards: #1e293b, Accent: #60a5fa
- Success: #065f46/#6ee7b7, Danger: #7f1d1d/#fca5a5
- Warning: #78350f/#fcd34d, Info: #1e3a8a/#93c5fd

web/api/scans.py

@@ -11,7 +11,8 @@ from sqlalchemy.exc import SQLAlchemyError
 
 from web.auth.decorators import api_auth_required
 from web.services.scan_service import ScanService
-from web.utils.validators import validate_config_file, validate_page_params
+from web.utils.validators import validate_config_file
+from web.utils.pagination import validate_page_params
 
 bp = Blueprint('scans', __name__)
 logger = logging.getLogger(__name__)