fix(dashboard): keep SSE alive + seed camera list via REST

The dashboard showed "No Cameras Connected" despite the API returning the
camera:
- middleware.Timeout + http.Server.WriteTimeout (10s) cancelled the
  long-lived /api/v1/events/stream every 10s, before any 30s status event
  could arrive — so the SSE-fed store never populated. Drop the global
  request timeout and set WriteTimeout=0 (closed-LAN kiosk).
- The SPA never seeded from GET /api/v1/cameras (SSE only pushes on change).
  Fetch the list once on mount and setCameras().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cmd/server/main.go

@@ -78,7 +78,9 @@ func main() {
 	r.Use(middleware.RealIP)
 	r.Use(middleware.Logger)
 	r.Use(middleware.Recoverer)
-	r.Use(middleware.Timeout(cfg.WriteTimeout))
+	// No global request timeout: it cancels the long-lived SSE stream
+	// (/api/v1/events/stream) — that's why the dashboard never received
+	// camera events. Closed-LAN kiosk, so dropping it is fine.
 
 	// Health check (no auth)
 	r.Get("/health", func(w http.ResponseWriter, r *http.Request) {
@@ -94,11 +96,12 @@ func main() {
 
 	// Create server
 	httpServer := &http.Server{
-		Addr:         ":" + cfg.Port,
-		Handler:      r,
-		ReadTimeout:  cfg.ReadTimeout,
-		WriteTimeout: cfg.WriteTimeout,
-		IdleTimeout:  cfg.IdleTimeout,
+		Addr:        ":" + cfg.Port,
+		Handler:     r,
+		ReadTimeout: cfg.ReadTimeout,
+		// WriteTimeout intentionally 0: SSE responses are long-lived and a
+		// write deadline would terminate them mid-stream.
+		IdleTimeout: cfg.IdleTimeout,
 	}
 
 	// Graceful shutdown