fix(i18n,api): backfill missing token-monitoring keys and fix JWT expiry tz

- i18n: add models.searchProviders, monitoring.tabs.tokens and the
  monitoring.tokens.* block (incl. bucket.hour/day) to es-ES, ja-JP,
  ru-RU, th-TH, vi-VN and zh-Hant, which were missing them and failed
  the Check i18n Keys CI.
- api: generate_jwt_token built 'exp' from a naive datetime.now(), which
  PyJWT validates against UTC — in any timezone ahead of UTC the token
  was already expired at issue time. Use datetime.now(timezone.utc).

src/langbot/pkg/api/http/service/user.py

@@ -82,7 +82,7 @@ class UserService:
         payload = {
             'user': user_email,
             'iss': 'LangBot-' + constants.edition,
-            'exp': datetime.datetime.now() + datetime.timedelta(seconds=jwt_expire),
+            'exp': datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(seconds=jwt_expire),
         }
 
         return jwt.encode(payload, jwt_secret, algorithm='HS256')