Fix prefix links on prefix length page with URL encoding

- Add urlEncode template function to properly encode prefix URLs
- Move prefix_length.html to embedded templates with function map
- Prevents broken links for prefixes containing slashes

internal/server/handlers.go

@@ -5,7 +5,6 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"html/template"
 	"net"
 	"net/http"
 	"net/url"
@@ -838,7 +837,7 @@ func (s *Server) handlePrefixLength() http.HandlerFunc {
 		default:
 		}
 
-		tmpl := template.Must(template.ParseFiles("internal/templates/prefix_length.html"))
+		tmpl := templates.PrefixLengthTemplate()
 		if err := tmpl.Execute(w, data); err != nil {
 			s.logger.Error("Failed to render prefix length template", "error", err)
 			http.Error(w, "Internal Server Error", http.StatusInternalServerError)