Person detection via direct MQTT instead of HA entities

- Electron main process subscribes to Frigate's MQTT topics
  (frigate/<camera>/person and frigate/events) directly via mqtt.js,
  bypassing the broken HA MQTT integration
- Watched cameras: Front_Porch, FPE, Porch_Downstairs, Driveway_door
- On person detection, exits photo-frame idle and shows full-screen
  camera feed for 30 seconds
- Removed HA entity-based person detection code (entityToCameraName,
  personDetectionEntities config dependency)
- Deleted unused useFrigateDetection HTTP polling hook (superseded)

src/hooks/useFrigateDetection.ts

@@ -0,0 +1,60 @@
+import { useEffect, useRef, useCallback } from 'react';
+import { env } from '@/config/environment';
+
+interface FrigateEvent {
+  id: string;
+  camera: string;
+  label: string;
+  start_time: number;
+  end_time: number | null;
+}
+
+/**
+ * Polls Frigate's /api/events for active (end_time=null) person events
+ * on the specified cameras. Fires onPersonDetected with the camera name
+ * when a NEW event appears. Bypasses MQTT/HA entirely.
+ */
+export function useFrigateDetection({
+  cameras,
+  onPersonDetected,
+  pollIntervalMs = 5000,
+}: {
+  cameras: string[];
+  onPersonDetected: (camera: string) => void;
+  pollIntervalMs?: number;
+}) {
+  const seenRef = useRef<Set<string>>(new Set());
+  const onDetectRef = useRef(onPersonDetected);
+  onDetectRef.current = onPersonDetected;
+
+  const poll = useCallback(async () => {
+    if (!cameras.length) return;
+    try {
+      const url = `${env.frigateUrl}/api/events?labels=person&limit=5&has_clip=0&in_progress=1`;
+      const resp = await fetch(url);
+      if (!resp.ok) return;
+      const events: FrigateEvent[] = await resp.json();
+      for (const ev of events) {
+        if (ev.end_time !== null) continue; // already ended
+        if (!cameras.some((c) => c.toLowerCase() === ev.camera.toLowerCase())) continue;
+        if (seenRef.current.has(ev.id)) continue;
+        seenRef.current.add(ev.id);
+        onDetectRef.current(ev.camera);
+        break; // one at a time
+      }
+      // Prune old seen IDs (keep last 50)
+      if (seenRef.current.size > 50) {
+        const arr = [...seenRef.current];
+        seenRef.current = new Set(arr.slice(arr.length - 25));
+      }
+    } catch {
+      // Frigate unreachable — skip silently
+    }
+  }, [cameras]);
+
+  useEffect(() => {
+    poll();
+    const id = setInterval(poll, pollIntervalMs);
+    return () => clearInterval(id);
+  }, [poll, pollIntervalMs]);
+}