feat: Add plain text CV endpoint and contact form with security

Plain text endpoint:
- Add /text route for plain text CV (for curl/AI crawlers)
- Use k3a/html2text library for HTML-to-text conversion
- Add Plain Text button to hamburger menu with UI translations

Contact form feature:
- Add ContactHandler with proper email service integration
- Add CSRF protection middleware
- Add rate limiting (5 submissions/hour per IP)
- Add honeypot and timing-based bot protection
- Add input validation with detailed error messages
- Add security logging middleware
- Add browser-only middleware for API protection

Code quality:
- Fix all golangci-lint errcheck warnings for w.Write calls
- Remove duplicate getClientIP functions
- Wire up ContactHandler in routes.Setup

.env.example

@@ -49,6 +49,19 @@ ALLOWED_ORIGINS=
 BEHIND_PROXY=false
 TRUSTED_PROXY_IP=
 
+# Email Configuration (Contact Form)
+# For Gmail:
+# 1. Enable 2FA in your Google account
+# 2. Go to https://myaccount.google.com/apppasswords
+# 3. Generate an App Password
+# 4. Use that password here (not your regular Gmail password)
+SMTP_HOST=smtp.gmail.com
+SMTP_PORT=587
+SMTP_USER=your-email@gmail.com
+SMTP_PASSWORD=your-app-password-here
+SMTP_FROM_EMAIL=your-email@gmail.com
+CONTACT_EMAIL=txeo.msx@gmail.com
+
 # Production Settings
 # Uncomment for production:
 # GO_ENV=production