feat: add HTML index page for browser viewing

Add a beautiful HTML landing page when visiting relay in browser:
- Shows all three protocol endpoints (gRPC, Connect, WebSocket)
- Lists supported NIPs (01, 09, 11)
- Displays relay features and info
- Responsive design with gradient styling
- Serves on GET requests (regular Accept header)
- NIP-11 still served for Accept: application/nostr+json

1 files changed, 24 insertions, 4 deletions

diff --git a/internal/handler/websocket/handler.go b/internal/handler/websocket/handler.go
index 224a2f8..2d531e9 100644
--- a/internal/handler/websocket/handler.go
+++ b/internal/handler/websocket/handler.go
@@ -21,8 +21,9 @@ type EventStore interface {
 }
 
 type Handler struct {
-        store EventStore
-        subs  *subscription.Manager
+        store     EventStore
+        subs      *subscription.Manager
+        indexData IndexData
 }
 
 func NewHandler(store EventStore, subs *subscription.Manager) *Handler {
@@ -32,9 +33,28 @@ func NewHandler(store EventStore, subs *subscription.Manager) *Handler {
         }
 }
 
+// SetIndexData sets the addresses for the index page
+func (h *Handler) SetIndexData(grpcAddr, httpAddr, wsAddr string) {
+        h.indexData = IndexData{
+                GrpcAddr: grpcAddr,
+                HttpAddr: httpAddr,
+                WsAddr:   wsAddr,
+        }
+}
+
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-        if r.Method == "GET" && r.Header.Get("Accept") == "application/nostr+json" {
-                h.ServeNIP11(w, r)
+        // Handle GET requests
+        if r.Method == "GET" {
+                accept := r.Header.Get("Accept")
+
+                // NIP-11: Relay information document
+                if accept == "application/nostr+json" {
+                        h.ServeNIP11(w, r)
+                        return
+                }
+
+                // Serve HTML index for browsers
+                h.ServeIndex(w, r, h.indexData)
                 return
         }