feat: intégration capteur CO2 MH-Z19

- Scripts MH-Z19/get_data.py (lecture standalone) et write_data.py (écriture SQLite)
- Table data_MHZ19, config MHZ19, cleanup et service systemd (120s)
- Web UI : carte test sensors, checkbox admin, boutons database + CSV download
- SARA_send_data_v2.py non modifié (sera fait dans un second temps)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sqlite/set_config.py

@@ -50,6 +50,7 @@ config_entries = [
     ("BME280", "1", "bool"),
     ("MPPT", "0", "bool"),
     ("NOISE", "0", "bool"),
+    ("MHZ19", "0", "bool"),
     ("modem_version", "XXX", "str"),
     ("device_type", "nebuleair_pro", "str"),
     ("language", "fr", "str"),