Issue 32: API Unit/Integration Test Parity

[laraibg786]

Goal

Verify that all API endpoints have equivalent unit and integration test coverage. Both test suites validate the same behavior; integration tests verify real database state, unit tests use mocks. No coverage gaps.

Requirements

Functional

• Audit all existing unit tests (Issue 01: FastAPI scaffold #1 to Issue 22: OpenAPI Spec and Postman Collection #22) and integration tests.
• Identify and document coverage gaps.
• Add missing unit tests (mocked DB) for all 13+ endpoints.
• Add missing integration tests (real DB + RLS) for all 13+ endpoints.
• Ensure all error codes (4xx, 5xx) have dedicated test cases.
• Verify RLS enforcement in integration tests (cross-vendor isolation).

Technical

• Coverage Matrix: All endpoints must have unit + integration + error case tests.
• Endpoints: POST /auth/signup, POST /auth/login, POST /auth/refresh, POST /licenses, GET /licenses, GET /licenses/{id}, PATCH /licenses/{id}, POST /licenses/{id}/revoke, POST /license-activation/validate, POST /licenses/{id}/activate/session, POST /licenses/heartbeat, GET /audit/export.csv, GET /health.
• Minimum: ~45 total test cases across all endpoints.

Acceptance Criteria

• All 13+ endpoints have both unit and integration tests.
• All error codes (4xx, 5xx) have dedicated test cases.
• RLS isolation verified in integration tests (Vendor A cannot see Vendor B's data).
• Coverage report shows >90%.
• All tests pass in CI.

Dependencies

• Blocked by: Issue 01: FastAPI scaffold #1 to Issue 22: OpenAPI Spec and Postman Collection #22 (all endpoints must exist).
• Blocks: Nothing (final quality gate).