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

data/ui-en.json

@@ -159,6 +159,34 @@
     "viewSource": "View Project in Github",
     "viewSourceSubtext": "Want to know how it's built?"
   },
+  "contactModal": {
+    "title": "Get in Touch",
+    "subtitle": "Let's connect!",
+    "description": "Have a question or interested in working together? Fill out the form below and I'll get back to you as soon as possible.",
+    "close": "Close",
+    "form": {
+      "email": "Email",
+      "emailPlaceholder": "your.email@example.com",
+      "name": "Name",
+      "namePlaceholder": "Your name",
+      "company": "Company",
+      "companyPlaceholder": "Company",
+      "subject": "Subject",
+      "subjectPlaceholder": "Subject",
+      "message": "Message",
+      "messagePlaceholder": "Your message...",
+      "submit": "Send Message",
+      "sending": "Sending...",
+      "note": "* Required fields"
+    },
+    "success": {
+      "title": "Message Sent!",
+      "message": "Thank you for your message. I'll get back to you soon."
+    },
+    "error": {
+      "title": "Error"
+    }
+  },
   "widgets": {
     "backToTop": {
       "ariaLabel": "Back to top",
@@ -196,9 +224,15 @@
       "title": "Preparing PDF",
       "closeLabel": "Close notification"
     },
+    "contact": {
+      "ariaLabel": "Contact me",
+      "tooltip": "Contact me"
+    },
     "actionButtons": {
       "downloadPdf": "Download as PDF",
-      "printFriendly": "Print Friendly"
+      "printFriendly": "Print Friendly",
+      "plainText": "Plain Text",
+      "contact": "Contact"
     }
   }
 }

data/ui-es.json

@@ -159,6 +159,34 @@
     "viewSource": "Ver proyecto en Github",
     "viewSourceSubtext": "¿Quieres saber cómo está hecho?"
   },
+  "contactModal": {
+    "title": "Ponerse en contacto",
+    "subtitle": "¡Conectemos!",
+    "description": "¿Tienes alguna pregunta o estás interesado en trabajar juntos? Rellena el formulario a continuación y me pondré en contacto contigo lo antes posible.",
+    "close": "Cerrar",
+    "form": {
+      "email": "Correo electrónico",
+      "emailPlaceholder": "tu.email@ejemplo.com",
+      "name": "Nombre",
+      "namePlaceholder": "Tu nombre",
+      "company": "Empresa",
+      "companyPlaceholder": "Empresa",
+      "subject": "Asunto",
+      "subjectPlaceholder": "Asunto",
+      "message": "Mensaje",
+      "messagePlaceholder": "Tu mensaje...",
+      "submit": "Enviar mensaje",
+      "sending": "Enviando...",
+      "note": "* Campos obligatorios"
+    },
+    "success": {
+      "title": "¡Mensaje enviado!",
+      "message": "Gracias por tu mensaje. Me pondré en contacto contigo pronto."
+    },
+    "error": {
+      "title": "Error"
+    }
+  },
   "widgets": {
     "backToTop": {
       "ariaLabel": "Volver arriba",
@@ -196,9 +224,15 @@
       "title": "Preparando PDF",
       "closeLabel": "Cerrar notificación"
     },
+    "contact": {
+      "ariaLabel": "Contáctame",
+      "tooltip": "Contáctame"
+    },
     "actionButtons": {
       "downloadPdf": "Descargar como PDF",
-      "printFriendly": "Imprimir amigable"
+      "printFriendly": "Imprimir amigable",
+      "plainText": "Texto Plano",
+      "contact": "Contacto"
     }
   }
 }