fix: stale display outputs leaking between pages in web UI

Bug: when the StreamDeck was on a non-main page (e.g. dashboard) and the
web UI was opened in a private browser tab, the frontend defaulted to the
first page in config while display outputs from the other page were still
applied to keys sharing the same index.

Fix 1 (backend): send the current active page via SSE immediately on new
client connection so the frontend knows the correct page from the start.

Fix 2 (frontend): only apply display output text/background to keys that
have a display config, preventing cross-page leakage.

static/app.js

@@ -181,8 +181,8 @@ document.addEventListener('alpine:init', () => {
           hasDisplay: !!(kc?.display),
           hasAction: !!(kc?.actions?.length),
           actionTypes: this.getActionTypes(kc?.actions || []),
-          displayBg: dout?.background || '',
-          displayText: dout?.text || '',
+          displayBg: (kc?.display && dout?.background) || '',
+          displayText: (kc?.display && dout?.text) || '',
           previewUrl: this.keyPreviewUrl(kc ? kc : {}, dout),
           isDynamic: !!(page.dynamic_keys && page.effective_keys?.find(k => k.index === i)),
         })
@@ -204,7 +204,7 @@ document.addEventListener('alpine:init', () => {
       const k = kc || {}
       let url = '/api/render?key_size=72'
       if (k.icon) url += `&icon=${encodeURIComponent(k.icon)}`
-      const label = dout?.text || this.displayOutputs[k.index]?.text || k.label
+      const label = (k.display && (dout?.text || this.displayOutputs[k.index]?.text)) || k.label
       if (label) url += `&label=${encodeURIComponent(label)}`
       if (k.icon_scale != null) url += `&icon_scale=${k.icon_scale}`
       if (k.font_size != null) url += `&font_size=${k.font_size}`

web.go

@@ -172,6 +172,14 @@ func (s *WebServer) handleSSE(w http.ResponseWriter, r *http.Request) {
 	s.sseClients[ch] = struct{}{}
 	s.sseMu.Unlock()
 
+	s.mu.RLock()
+	if s.pm != nil {
+		if active := s.pm.ActivePageName(); active != "" {
+			ch <- active
+		}
+	}
+	s.mu.RUnlock()
+
 	notify := r.Context().Done()
 	go func() {
 		<-notify