fix: pass resource param in M2M token request for JWT issuance

[raghavyuva]

Summary

• getM2MToken() was not passing the resource parameter in the client_credentials token request
• Without resource, the auth service returns an opaque token instead of a JWT
• The Nixopus API requires a JWT for M2M auth validation via JWKS, so opaque tokens silently fail and fall through to session auth (401)
• Now passes config.apiUrl as resource so the token is issued as a JWT with the correct audience

Test plan

• Ensure API_URL is set in the agent's environment (e.g. https://api.nixopus.com/api or http://nixopus-api:8443)
• Ensure the API URL is included in M2M_AUDIENCES on the auth service
• Fire an incident event and verify the agent successfully calls back to the API (no more 401)