Add /notify endpoint for Home Assistant integration

- New /notify endpoint: simple {"message": "", "duration": 5} API
- Uses Priority 3 (Notify) with auto-expiring TTL
- Updated CLAUDE.md with HA integration examples
- Updated README.md with new features and endpoints
- Added Docker detector to documentation
- Removed completed TODO items

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

aggregator.py

@@ -223,6 +223,34 @@ def clear_event():
             return jsonify({"error": "Event not found"}), 404
 
 
+@app.route("/notify", methods=["POST"])
+def notify():
+    """
+    Simple notification endpoint for Home Assistant.
+    JSON: {"message": "text", "duration": 5}
+    Shows the Notify emote with message, auto-expires after duration.
+    """
+    data = request.get_json(force=True) if request.data else {}
+    message = data.get("message", "")
+    duration = int(data.get("duration", 5))
+
+    # Generate unique ID to avoid conflicts
+    event_id = f"ha_notify_{int(time.time() * 1000)}"
+
+    event = {
+        "priority": 3,  # Notify priority
+        "message": message,
+        "timestamp": time.time(),
+        "ttl": time.time() + duration,
+    }
+
+    with events_lock:
+        active_events[event_id] = event
+
+    state = write_status()
+    return jsonify({"status": "ok", "id": event_id, "current_state": state}), 200
+
+
 @app.route("/sleep", methods=["POST"])
 def sleep_mode():
     """Enter sleep mode. For Home Assistant webhook."""