Fix prefix URL routing by using URL encoding

- Replace slash-to-dash conversion with proper URL encoding
- Update handlePrefixDetail and handlePrefixDetailJSON to URL decode prefix parameter
- Update handleIPRedirect to URL encode the prefix in the redirect
- Add urlEncode template function for use in templates
- Update AS detail template to URL encode prefix links
- This properly handles the slash in CIDR notation (e.g., /prefix/192.168.1.0%2F24)

internal/templates/as_detail.html

@@ -178,7 +178,7 @@
                 <tbody>
                     {{range .IPv4Prefixes}}
                     <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>/{{.MaskLength}}</td>
                         <td>{{.LastUpdated.Format "2006-01-02 15:04:05"}}</td>
                         <td class="age">{{.LastUpdated | timeSince}}</td>
@@ -207,7 +207,7 @@
                 <tbody>
                     {{range .IPv6Prefixes}}
                     <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>/{{.MaskLength}}</td>
                         <td>{{.LastUpdated.Format "2006-01-02 15:04:05"}}</td>
                         <td class="age">{{.LastUpdated | timeSince}}</td>

internal/templates/templates.go

@@ -4,6 +4,7 @@ package templates
 import (
 	_ "embed"
 	"html/template"
+	"net/url"
 	"sync"
 	"time"
 )
@@ -78,6 +79,7 @@ func initTemplates() {
 	// Create common template functions
 	funcs := template.FuncMap{
 		"timeSince": timeSince,
+		"urlEncode": url.QueryEscape,
 	}
 
 	// Parse status template