[jmgasper]

Opening an opportunity in Sales returns 502: Unable to load opportunity billing accounts because Projects API never initializes its outbound M2M client. The released tc-core-library-js v4 exposes createM2MClient at the top level, but the constructor still checks the removed auth.m2m export and skips initialization.

Initialize the client directly through the typed factory so billing-account lookups can obtain a machine token. Existing Auth0 endpoint, proxy, audience, credential lookup, and token-error behavior are preserved. Invalid endpoint configuration now fails during service construction instead of leaving a silently uninitialized client.

Validation:

• Added tests using the installed tc-core library and a local token endpoint for token acquisition/caching, missing credentials, and upstream rejection. All three reproduced the old initialization failure before the fix and pass afterward.
• Full Jest suite on Node 26: 532 passed, 3 skipped (66 passing suites).
• Nest production build, ESLint on changed files, and git diff --check passed.
• No production credentials or external token endpoints were used in tests.

Deployment: deploy Projects API after merging, then verify that opening a Sales opportunity loads its details and billing context. No configuration or database migration is required. Live recovery remains to be verified after deployment.