feat: add per-device check button on WLED devices page

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

app.py

@@ -256,6 +256,27 @@ async def check_all_devices():
     return RedirectResponse("/devices", status_code=303)
 
 
+@app.post("/api/devices/{device_id}/check")
+async def check_single_device(device_id: int):
+    from wled_client import get_wled_info
+    conn = database.get_db()
+    dev = conn.execute("SELECT hostname FROM wled_devices WHERE id=?", (device_id,)).fetchone()
+    if dev:
+        from datetime import datetime
+        info = get_wled_info(dev["hostname"])
+        conn.execute("""
+            UPDATE wled_devices SET online=?, leds=?, version=?, last_check=? WHERE id=?
+        """, (
+            1 if info.get("online") else 0,
+            info.get("leds", 0) if info.get("online") else 0,
+            info.get("version", "") if info.get("online") else "",
+            datetime.now(), device_id,
+        ))
+        conn.commit()
+    conn.close()
+    return RedirectResponse("/devices", status_code=303)
+
+
 # ── Assignments ────────────────────────────────────────────────────────────
 
 @app.get("/assignments", response_class=HTMLResponse)