feat: show last activity timestamp per device on Tuerschilder page

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app.py

@@ -202,9 +202,20 @@ async def toggle_user(azure_id: str):
 @app.get("/devices", response_class=HTMLResponse)
 async def devices_page(request: Request):
     conn = database.get_db()
-    devices = conn.execute(
+    devices_raw = conn.execute(
         "SELECT * FROM wled_devices ORDER BY name, hostname"
     ).fetchall()
+    # Letzte Aktivitaet pro Device aus activity_log
+    devices = []
+    for dev in devices_raw:
+        last_act = conn.execute("""
+            SELECT MAX(l.timestamp) as la
+            FROM activity_log l
+            WHERE l.wled_url LIKE '%' || ? || '%'
+        """, (dev["hostname"],)).fetchone()
+        d = dict(dev)
+        d["last_activity"] = last_act["la"] if last_act and last_act["la"] else None
+        devices.append(d)
     last_check_row = conn.execute(
         "SELECT MAX(last_check) as lc FROM wled_devices WHERE last_check IS NOT NULL"
     ).fetchone()