Complete Phase 7: Polish & Cross-Cutting Concerns

This commit implements all remaining polish tasks (T193-T210) to make
the application production-ready.

## Logging & Monitoring (T193, T194, T208, T209)
- Add structured JSON logging for production environments
- Add human-readable logging for development
- Implement comprehensive error logging across all routes:
  * submission.py: product access, validation, success/failure
  * auth.py: login attempts, successes, failures, logouts
  * dashboard.py: access and errors
- Add /health endpoint for monitoring (checks data dir, API key)
- Add environment variable validation on startup

## Security Hardening (T196-T199, T207)
- Add HSTS headers in production (1 year, includeSubDomains)
- Add security headers: X-Content-Type-Options, X-Frame-Options, X-XSS-Protection
- Verify CSRF protection on all POST routes (Flask-WTF)
- Verify session cookie security flags (HttpOnly, Secure, SameSite)
- Verify XSS prevention (Jinja2 auto-escaping)
- Verify no hardcoded secrets (only in test files)

## Documentation (T195, T203, T210)
- Add comprehensive README.md with:
  * Features, quick start, project structure
  * Usage guides (end users, product owners, admins)
  * Configuration, testing, deployment instructions
- Add detailed docs/deployment.md with:
  * Production deployment steps
  * ClamAV, Nginx, SSL/TLS setup
  * Security hardening, monitoring, backup strategies
- Add requirements-dev.txt for development dependencies

## Performance Testing (T200, T201)
- Add test_performance.py with 4 comprehensive tests:
  * 100 concurrent submissions (SC-012)
  * Dashboard load <3s for 1000 items (SC-008)
  * Large file upload handling
  * Rate limiting verification
- Add performance marker to pytest.ini

## Testing
- All 49 tests passing, 1 skipped
- Fixed error handling to preserve HTTP status codes

Phase 7 complete. Application is production-ready with comprehensive
logging, security, monitoring, and documentation.

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

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

app/routes/auth.py

@@ -1,6 +1,6 @@
 """Authentication routes"""
-from flask import Blueprint, render_template, request, redirect, url_for, flash
-from flask_login import login_user, logout_user, login_required
+from flask import Blueprint, render_template, request, redirect, url_for, flash, current_app
+from flask_login import login_user, logout_user, login_required, current_user
 from app.models.user import User
 
 
@@ -19,6 +19,7 @@ def login():
         password = request.form.get('password', '')
 
         if not username or not password:
+            current_app.logger.warning('Login attempt with missing credentials')
             flash('Please provide both username and password', 'error')
             return render_template('auth/login.html')
 
@@ -26,11 +27,13 @@ def login():
 
         if user and user.is_active and user.check_password(password):
             login_user(user)
+            current_app.logger.info(f'User logged in successfully: {username} (role: {user.role})')
             flash(f'Welcome back, {user.username}!', 'success')
 
             # Redirect to dashboard for product owners and administrators
             return redirect(url_for('dashboard.list'))
         else:
+            current_app.logger.warning(f'Failed login attempt for username: {username}')
             flash('Invalid username or password', 'error')
 
     return render_template('auth/login.html')
@@ -40,6 +43,8 @@ def login():
 @login_required
 def logout():
     """User logout"""
+    username = current_user.username
     logout_user()
+    current_app.logger.info(f'User logged out: {username}')
     flash('You have been logged out', 'info')
     return redirect(url_for('index'))