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

internal/models/ui/ui.go

@@ -12,6 +12,7 @@ type UI struct {
 	PdfModal       PdfModal       `json:"pdfModal"`
 	ShortcutsModal ShortcutsModal `json:"shortcutsModal"`
 	InfoModal      InfoModal      `json:"infoModal"`
+	ContactModal   ContactModal   `json:"contactModal"`
 	Widgets        Widgets        `json:"widgets"`
 }
 
@@ -142,6 +143,38 @@ type TechStack struct {
 	CSS3   string `json:"css3"`
 }
 
+// ContactModal labels
+type ContactModal struct {
+	Title       string           `json:"title"`
+	Subtitle    string           `json:"subtitle"`
+	Description string           `json:"description"`
+	Close       string           `json:"close"`
+	Form        ContactFormLabel `json:"form"`
+	Success     ContactResult    `json:"success"`
+	Error       ContactResult    `json:"error"`
+}
+
+type ContactFormLabel struct {
+	Email            string `json:"email"`
+	EmailPlaceholder string `json:"emailPlaceholder"`
+	Name             string `json:"name"`
+	NamePlaceholder  string `json:"namePlaceholder"`
+	Company          string `json:"company"`
+	CompanyPlaceholder string `json:"companyPlaceholder"`
+	Subject          string `json:"subject"`
+	SubjectPlaceholder string `json:"subjectPlaceholder"`
+	Message          string `json:"message"`
+	MessagePlaceholder string `json:"messagePlaceholder"`
+	Submit           string `json:"submit"`
+	Sending          string `json:"sending"`
+	Note             string `json:"note"`
+}
+
+type ContactResult struct {
+	Title   string `json:"title"`
+	Message string `json:"message,omitempty"`
+}
+
 // Widget label types
 type Widgets struct {
 	BackToTop     WidgetLabel        `json:"backToTop"`
@@ -152,6 +185,7 @@ type Widgets struct {
 	ZoomToggle    WidgetLabel        `json:"zoomToggle"`
 	ZoomControl   ZoomControlLabel   `json:"zoomControl"`
 	PdfToast      PdfToastLabel      `json:"pdfToast"`
+	Contact       WidgetLabel        `json:"contact"`
 	ActionButtons ActionButtonsLabel `json:"actionButtons"`
 }
 
@@ -177,4 +211,6 @@ type PdfToastLabel struct {
 type ActionButtonsLabel struct {
 	DownloadPdf   string `json:"downloadPdf"`
 	PrintFriendly string `json:"printFriendly"`
+	PlainText     string `json:"plainText"`
+	Contact       string `json:"contact"`
 }