feat: add Udemy courses and fix footer i18n + golangci-lint errors

- Add 5 Udemy courses with PDF certificate links (Go, Fyne, HTMX)
- Fix cv-footer.html to use CV data instead of hardcoded values
- Add i18n labels for footer (linkedin, github, domestika, email, phone)
- Fix 11 golangci-lint errors:
  - errcheck: proper Close() error handling in email/security/tests
  - staticcheck: simplify return and merge variable declaration
  - unused: remove legacy sendEmail and formatMessage functions

internal/handlers/cv_text.go

@@ -44,11 +44,7 @@ func isTextBrowser(r *http.Request) bool {
 
 	// Check Accept header - if client prefers text/plain
 	accept := r.Header.Get("Accept")
-	if strings.HasPrefix(accept, "text/plain") {
-		return true
-	}
-
-	return false
+	return strings.HasPrefix(accept, "text/plain")
 }
 
 // ==============================================================================
@@ -72,10 +68,7 @@ func (h *CVHandler) PlainText(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Check icons parameter (default: true)
-	showIcons := true
-	if r.URL.Query().Get("icons") == "false" {
-		showIcons = false
-	}
+	showIcons := r.URL.Query().Get("icons") != "false"
 
 	// Prepare template data using shared helper (loads CV data)
 	data, err := h.prepareTemplateData(langCode)

internal/middleware/security_logger.go

@@ -132,7 +132,11 @@ func logToSecurityFile(eventJSON []byte) {
 		log.Printf("WARNING: Failed to open security log file: %v", err)
 		return
 	}
-	defer f.Close()
+	defer func() {
+		if err := f.Close(); err != nil {
+			log.Printf("WARNING: Failed to close security log file: %v", err)
+		}
+	}()
 
 	// Write event with newline
 	if _, err := f.Write(eventJSON); err != nil {

internal/models/ui/ui.go

@@ -102,6 +102,11 @@ type Sections struct {
 type Footer struct {
 	ViewOnGithub string `json:"viewOnGithub"`
 	LastUpdated  string `json:"lastUpdated"`
+	Linkedin     string `json:"linkedin"`
+	Github       string `json:"github"`
+	Domestika    string `json:"domestika"`
+	Email        string `json:"email"`
+	Phone        string `json:"phone"`
 }
 
 // Portfolio labels

internal/services/email.go

@@ -224,74 +224,7 @@ func (e *EmailService) sendMultipartEmail(subject, htmlBody, textBody, replyTo s
 	if err != nil {
 		return fmt.Errorf("failed to connect to SMTP server: %w", err)
 	}
-	defer client.Close()
-
-	// Authenticate
-	if err = client.Auth(auth); err != nil {
-		return fmt.Errorf("SMTP authentication failed: %w", err)
-	}
-
-	// Set sender and recipient
-	if err = client.Mail(from); err != nil {
-		return fmt.Errorf("failed to set sender: %w", err)
-	}
-	if err = client.Rcpt(to); err != nil {
-		return fmt.Errorf("failed to set recipient: %w", err)
-	}
-
-	// Send message
-	w, err := client.Data()
-	if err != nil {
-		return fmt.Errorf("failed to get data writer: %w", err)
-	}
-
-	_, err = w.Write([]byte(message))
-	if err != nil {
-		return fmt.Errorf("failed to write message: %w", err)
-	}
-
-	err = w.Close()
-	if err != nil {
-		return fmt.Errorf("failed to close writer: %w", err)
-	}
-
-	return client.Quit()
-}
-
-// sendEmail sends an email using SMTP (plain text only - legacy)
-func (e *EmailService) sendEmail(subject, body string) error {
-	// Validate config
-	if e.config.SMTPHost == "" || e.config.SMTPPort == "" {
-		return fmt.Errorf("SMTP configuration incomplete")
-	}
-	if e.config.SMTPUser == "" || e.config.SMTPPassword == "" {
-		return fmt.Errorf("SMTP credentials missing")
-	}
-	if e.config.ToEmail == "" {
-		return fmt.Errorf("recipient email not configured")
-	}
-
-	// Build email message
-	from := e.config.FromEmail
-	if from == "" {
-		from = e.config.SMTPUser
-	}
-
-	to := e.config.ToEmail
-	message := e.formatMessage(from, to, subject, body)
-
-	// SMTP server address
-	addr := fmt.Sprintf("%s:%s", e.config.SMTPHost, e.config.SMTPPort)
-
-	// Setup authentication
-	auth := smtp.PlainAuth("", e.config.SMTPUser, e.config.SMTPPassword, e.config.SMTPHost)
-
-	// Connect to SMTP server with TLS
-	client, err := e.connectSMTP(addr)
-	if err != nil {
-		return fmt.Errorf("failed to connect to SMTP server: %w", err)
-	}
-	defer client.Close()
+	defer func() { _ = client.Close() }()
 
 	// Authenticate
 	if err = client.Auth(auth); err != nil {
@@ -342,7 +275,7 @@ func (e *EmailService) connectSMTP(addr string) (*smtp.Client, error) {
 		}
 		client, err := smtp.NewClient(conn, e.config.SMTPHost)
 		if err != nil {
-			conn.Close()
+			_ = conn.Close()
 			return nil, fmt.Errorf("SMTP client creation failed: %w", err)
 		}
 		return client, nil
@@ -411,23 +344,3 @@ func (e *EmailService) formatMultipartMessage(from, to, replyTo, subject, htmlBo
 
 	return message.String()
 }
-
-// formatMessage formats an email message with proper headers (plain text only)
-func (e *EmailService) formatMessage(from, to, subject, body string) string {
-	headers := make(map[string]string)
-	headers["From"] = from
-	headers["To"] = to
-	headers["Subject"] = subject
-	headers["MIME-Version"] = "1.0"
-	headers["Content-Type"] = "text/plain; charset=\"utf-8\""
-	headers["Date"] = time.Now().Format(time.RFC1123Z)
-
-	var message strings.Builder
-	for k, v := range headers {
-		message.WriteString(fmt.Sprintf("%s: %s\r\n", k, v))
-	}
-	message.WriteString("\r\n")
-	message.WriteString(body)
-
-	return message.String()
-}