Add admin dashboard at / with bearer-token overview API

internal/server/bridge.go

@@ -82,6 +82,41 @@ func (h *Hub) DrainAll() {
 	}
 }
 
+// BridgeInfo is a snapshot of one attached bridge for the admin API.
+type BridgeInfo struct {
+	Session       string
+	TunnelID      string
+	ClientVersion string
+	Routes        []string
+	Visitors      int
+	MaxConns      int
+	ConnectedAt   time.Time
+}
+
+// BridgeInfos snapshots every attached bridge. Field reads are safe without
+// the bridge lock because they are immutable after construction; only the
+// visitor count needs the lock.
+func (h *Hub) BridgeInfos() []BridgeInfo {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	out := make([]BridgeInfo, 0, len(h.bridges))
+	for b := range h.bridges {
+		b.mu.Lock()
+		visitors := len(b.conns)
+		b.mu.Unlock()
+		out = append(out, BridgeInfo{
+			Session:       b.session,
+			TunnelID:      b.tunnelID,
+			ClientVersion: b.clientVersion,
+			Routes:        b.routes,
+			Visitors:      visitors,
+			MaxConns:      b.maxConns,
+			ConnectedAt:   b.startedAt,
+		})
+	}
+	return out
+}
+
 func (h *Hub) register(b *Bridge) bool {
 	h.mu.Lock()
 	defer h.mu.Unlock()
@@ -128,6 +163,9 @@ type Bridge struct {
 	maxConns int
 	ws       *websocket.Conn
 
+	clientVersion string
+	startedAt     time.Time
+
 	outbox    chan outbound
 	done      chan struct{}
 	closeOnce sync.Once
@@ -198,15 +236,17 @@ func (h *Hub) attach(w http.ResponseWriter, r *http.Request, tunnel storedTunnel
 	}
 
 	b := &Bridge{
-		hub:      h,
-		tunnelID: tunnel.ID,
-		session:  sessionID(),
-		routes:   routes,
-		maxConns: maxConnsPerBridge,
-		ws:       ws,
-		outbox:   make(chan outbound, 256),
-		done:     make(chan struct{}),
-		conns:    map[uint32]*visitorConn{},
+		hub:           h,
+		tunnelID:      tunnel.ID,
+		session:       sessionID(),
+		routes:        routes,
+		maxConns:      maxConnsPerBridge,
+		ws:            ws,
+		clientVersion: attach.Client.Version,
+		startedAt:     time.Now(),
+		outbox:        make(chan outbound, 256),
+		done:          make(chan struct{}),
+		conns:         map[uint32]*visitorConn{},
 	}
 	if attach.Client.MaxConns > 0 && attach.Client.MaxConns < b.maxConns {
 		b.maxConns = attach.Client.MaxConns