feat: OTA firmware update per device with auto config backup

- Upload .bin firmware files via web UI
- Update individual devices (button per device in table)
- Auto config backup before each update
- Shows current version vs available firmware
- Firmware file management (upload/delete)

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

wled_client.py

@@ -69,3 +69,19 @@ def restore_wled_config(hostname, config_json):
         return r.status_code == 200, f"{r.status_code} {r.reason}"
     except requests.exceptions.RequestException as e:
         return False, str(e)
+
+
+def ota_update_wled(hostname, firmware_path):
+    """Push firmware binary to WLED device via OTA. Returns (success, message)."""
+    try:
+        with open(firmware_path, "rb") as f:
+            r = requests.post(
+                f"http://{hostname}/update",
+                files={"update": ("firmware.bin", f, "application/octet-stream")},
+                timeout=120,
+            )
+        if r.status_code == 200:
+            return True, "Update erfolgreich, Geraet startet neu"
+        return False, f"{r.status_code} {r.reason}"
+    except requests.exceptions.RequestException as e:
+        return False, str(e)