add a couple of things

fetcher.py

@@ -1,5 +1,4 @@
-import json
-from re import error
+from typing import Any, cast
 import ovh
 
 
@@ -10,13 +9,21 @@ def fetch_api(app_key: str, app_secret: str, consumer_key: str) -> list[str]:
         application_secret=app_secret,
         consumer_key=consumer_key,
     )
-    bills = client.get("/me/bill/")
+    data: Any = client.get("/me/bill/")
+
+    if data is None:
+        return []
+
+    if not isinstance(data, list) or not all(isinstance(x, str) for x in data):
+        raise TypeError("Réponse OVH inattendue pour /me/bill/: liste de str requise")
+
+    bills: list[str] = cast(list[str], data)
     return bills
 
 
 def fetch_invoice_content(
     id: str, app_key: str, app_secret: str, consumer_key: str
-) -> dict:
+) -> dict[str, Any]:
     client = ovh.Client(
         endpoint="ovh-eu",
         application_key=app_key,
@@ -24,4 +31,6 @@ def fetch_invoice_content(
         consumer_key=consumer_key,
     )
     bill = client.get(f"/me/bill/{id}")
+    if bill is None:
+        raise RuntimeError(f"Facture {id} introuvable")
     return bill