Phase 2 Step 4: Implement Authentication System

Implemented comprehensive Flask-Login authentication with single-user support.

New Features:
- Flask-Login integration with User model
- Bcrypt password hashing via PasswordManager
- Login, logout, and initial password setup routes
- @login_required and @api_auth_required decorators
- All API endpoints now require authentication
- Bootstrap 5 dark theme UI templates
- Dashboard with navigation
- Remember me and next parameter redirect support

Files Created (12):
- web/auth/__init__.py, models.py, decorators.py, routes.py
- web/routes/__init__.py, main.py
- web/templates/login.html, setup.html, dashboard.html, scans.html, scan_detail.html
- tests/test_authentication.py (30+ tests)

Files Modified (6):
- web/app.py: Added Flask-Login initialization and main routes
- web/api/scans.py: Protected all endpoints with @api_auth_required
- web/api/settings.py: Protected all endpoints with @api_auth_required
- web/api/schedules.py: Protected all endpoints with @api_auth_required
- web/api/alerts.py: Protected all endpoints with @api_auth_required
- tests/conftest.py: Added authentication test fixtures

Security:
- Session-based authentication for both web UI and API
- Secure password storage with bcrypt
- Protected routes redirect to login page
- Protected API endpoints return 401 Unauthorized
- Health check endpoints remain accessible for monitoring

Testing:
- User model authentication and properties
- Login success/failure flows
- Logout and session management
- Password setup workflow
- API endpoint authentication requirements
- Session persistence and remember me functionality
- Next parameter redirect behavior

Total: ~1,200 lines of code added

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

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

web/routes/main.py

@@ -0,0 +1,68 @@
+"""
+Main web routes for SneakyScanner.
+
+Provides dashboard and scan viewing pages.
+"""
+
+import logging
+
+from flask import Blueprint, current_app, redirect, render_template, url_for
+
+from web.auth.decorators import login_required
+
+logger = logging.getLogger(__name__)
+
+bp = Blueprint('main', __name__)
+
+
+@bp.route('/')
+def index():
+    """
+    Root route - redirect to dashboard.
+
+    Returns:
+        Redirect to dashboard
+    """
+    return redirect(url_for('main.dashboard'))
+
+
+@bp.route('/dashboard')
+@login_required
+def dashboard():
+    """
+    Dashboard page - shows recent scans and statistics.
+
+    Returns:
+        Rendered dashboard template
+    """
+    # TODO: Phase 5 - Add dashboard stats and recent scans
+    return render_template('dashboard.html')
+
+
+@bp.route('/scans')
+@login_required
+def scans():
+    """
+    Scans list page - shows all scans with pagination.
+
+    Returns:
+        Rendered scans list template
+    """
+    # TODO: Phase 5 - Implement scans list page
+    return render_template('scans.html')
+
+
+@bp.route('/scans/<int:scan_id>')
+@login_required
+def scan_detail(scan_id):
+    """
+    Scan detail page - shows full scan results.
+
+    Args:
+        scan_id: Scan ID to display
+
+    Returns:
+        Rendered scan detail template
+    """
+    # TODO: Phase 5 - Implement scan detail page
+    return render_template('scan_detail.html', scan_id=scan_id)