chore: move default idp domain

.env

@@ -5,7 +5,7 @@ STYLESHEET_URL: https://unpkg.com/bamboo.css
 CALLBACK_URL: /login-callback
 MCP_CLIENT_ID: client_id
 MCP_CLIENT_SECRET: client_secret
-MCP_PROVIDER: https://app-test.moncomptepro.beta.gouv.fr/
+MCP_PROVIDER: https://app-sandbox.moncomptepro.beta.gouv.fr/
 MCP_SCOPES: "openid email profile organization"
 LOGIN_HINT: ""
 MCP_ID_TOKEN_SIGNED_RESPONSE_ALG: RS256