Fix prefix URL routing for encoded CIDR notation

Change route from wildcard /prefix/* to explicit /prefix/{prefix}/{len}
to properly handle URL-encoded IPv6 addresses with CIDR notation.

- Separate prefix and length into individual path parameters
- Add prefixURL template function for generating correct links
- Remove url.QueryUnescape from handlers (chi handles decoding)

internal/server/routes.go

@@ -28,7 +28,7 @@ func (s *Server) setupRoutes() {
 
 	// AS and prefix detail pages
 	r.Get("/as/{asn}", s.handleASDetail())
-	r.Get("/prefix/*", s.handlePrefixDetail())
+	r.Get("/prefix/{prefix}/{len}", s.handlePrefixDetail())
 	r.Get("/prefixlength/{length}", s.handlePrefixLength())
 	r.Get("/prefixlength6/{length}", s.handlePrefixLength6())
 
@@ -45,7 +45,7 @@ func (s *Server) setupRoutes() {
 		r.Get("/stats", s.handleStats())
 		r.Get("/ip/{ip}", s.handleIPLookup())
 		r.Get("/as/{asn}", s.handleASDetailJSON())
-		r.Get("/prefix/*", s.handlePrefixDetailJSON())
+		r.Get("/prefix/{prefix}/{len}", s.handlePrefixDetailJSON())
 	})
 
 	s.router = r