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/templates/prefix_length.html

@@ -93,7 +93,7 @@
         <tbody>
             {{ range .Prefixes }}
             <tr>
-                <td><a href="/prefix/{{ .Prefix }}" class="prefix-link">{{ .Prefix }}</a></td>
+                <td><a href="/prefix/{{ .Prefix | urlEncode }}" class="prefix-link">{{ .Prefix }}</a></td>
                 <td class="age">{{ .Age }}</td>
                 <td>
                     <a href="/as/{{ .OriginASN }}" class="as-link">

internal/templates/templates.go

@@ -18,11 +18,15 @@ var asDetailHTML string
 //go:embed prefix_detail.html
 var prefixDetailHTML string
 
+//go:embed prefix_length.html
+var prefixLengthHTML string
+
 // Templates contains all parsed templates
 type Templates struct {
 	Status       *template.Template
 	ASDetail     *template.Template
 	PrefixDetail *template.Template
+	PrefixLength *template.Template
 }
 
 var (
@@ -99,6 +103,12 @@ func initTemplates() {
 	if err != nil {
 		panic("failed to parse prefix detail template: " + err.Error())
 	}
+
+	// Parse prefix length template
+	defaultTemplates.PrefixLength, err = template.New("prefixLength").Funcs(funcs).Parse(prefixLengthHTML)
+	if err != nil {
+		panic("failed to parse prefix length template: " + err.Error())
+	}
 }
 
 // Get returns the singleton Templates instance
@@ -122,3 +132,8 @@ func ASDetailTemplate() *template.Template {
 func PrefixDetailTemplate() *template.Template {
 	return Get().PrefixDetail
 }
+
+// PrefixLengthTemplate returns the parsed prefix length template
+func PrefixLengthTemplate() *template.Template {
+	return Get().PrefixLength
+}