[Fix] Surface API errors in logs and return MCP validation failures as 400s

[mrubens]

What changed

• apps/api/src/server.ts: the app-level onError handler now logs unexpected errors server-side (console.error with request method, path, and the error with stack) before responding, for both HTTPException >= 500 and generic errors. Sentry capture is unchanged.
• apps/api/src/handlers/custom-automations/index.ts: the create, update, and resolve-schedule MCP routes now translate expected validation failures thrown as plain Errors (missing environment, cron/schedule validation, automation cap, target configuration, etc.) into 400 responses carrying the message. Postgres duplicate-name unique violations (code 23505 on custom_automations_name_unique_idx, including drizzle-wrapped causes) return a friendly "A custom automation with this name already exists." message. Anything not on the known-pattern allowlist is rethrown so the app-level handler logs it and returns an opaque 500.
• Added apps/api/src/handlers/custom-automations/__tests__/custom-automations-routes.test.ts covering the 400 translations (missing environment, duplicate name direct and cause-wrapped, automation cap, schedule validation) and the rethrow-to-500 path for create, update, and resolve-schedule.

Why this change was made

• A 500 from the API previously left zero server-side trace when Sentry was not enabled (the local-dev default), since captureApiException is a no-op in that case.
• The admin-only custom-automations MCP surface returned a bare internal_server_error for expected validation failures, so the calling agent could not see what was wrong or self-correct. The web tRPC layer already surfaces these same messages to admins.

Impact

• Every unexpected API 500 now appears in the server logs with request context and a stack trace.
• Agents using manage_custom_automations get actionable 400 messages for expected failures instead of opaque 500s; truly unexpected errors still return 500 and are now logged.

[roomote-community]

No new code issues found. See task

• apps/api/src/handlers/custom-automations/index.ts:87-91 treats any PostgreSQL 23505 as this name conflict. Require custom_automations_name_unique_idx too, otherwise an unrelated unique-constraint failure is misreported as a duplicate automation and bypasses 500 logging.

_{Reviewed 6acd98c}