test: add unified auth integration coverage

[Zetazzz]

Summary

• Replace the temporary SQL runtime contract with a real generated Constructive DB application.
• Seed the current capabilities_module baseline and run PostgreSQL-backed OAuth/SSO integration tests.
• Forward the Constructive DB application path through the existing 12-factor environment layer.
• Keep the mock contract.sql removed.

Stack

Base: #1688
This is the final PR in the seven-PR implementation stack.

Cross-repository pin

Constructive DB PR #3009 commit: ffc87bb07ede49a0734f676d0eb06042f0565eef

Validation

• Real generated DB to PostgreSQL to GraphQL/OAuth HTTP integration: 1 suite, 4 tests passed
• express-context: 5 suites, 37 tests passed
• affected package builds passed
• git diff --check passed