Harden local runtime safety and error handling

internal/handlers/web.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"fmt"
 	"html/template"
 	"strconv"
 	"strings"
@@ -114,12 +115,14 @@ func (h *WebHandler) render(c *gin.Context, name string, data gin.H) {
 	c.Header("Content-Type", "text/html; charset=utf-8")
 	tmpl, ok := h.templates[name]
 	if !ok {
-		c.String(500, "Template not found: %s", name)
+		_ = c.Error(fmt.Errorf("template %q not found", name))
+		c.String(500, "Template error")
 		return
 	}
 	// Execute the page template which will use base
 	if err := tmpl.ExecuteTemplate(c.Writer, name, data); err != nil {
-		c.String(500, "Template error: %v", err)
+		_ = c.Error(err)
+		c.String(500, "Template error")
 	}
 }