feat(multitenancy): add modular foundation and PostgreSQL persistence (P1-P2)

[Adel7418]

Summary

This is the first pull request in the multi-tenant platform chain. It brings the already-reviewed P1 modular foundation and P2 PostgreSQL persistence onto master.

• add application factory, request/error/redaction boundaries, dependency seams and modular repositories
• add PostgreSQL 17 dev/test composition, SQLAlchemy/psycopg/Alembic infrastructure and restricted owner/runtime roles
• add restart-safe audit persistence, durable idempotency and PostgreSQL-backed draft/package stores
• add migration, backup/restore and isolated real-PostgreSQL verification coverage

Scope note

feat/multitenant-p2-postgresql contains three reviewed commits because P1 is not independently present on master:

• 53d8c6c — P1 modular multi-tenant foundation
• 3bf4c3a — P2 PostgreSQL persistence foundation
• a0971c1 — explicit audit delegation correction

P3 identity/tenancy is intentionally excluded and follows in stacked PR #23 targeting this branch.

Verification

• P1 full suite: 743 passed, 1 skipped
• P2 full suite: 762 passed, 1 skipped
• independent P2 focused real-PostgreSQL suite: 18 passed
• Ruff, mypy, compileall, OpenAPI sync, secret scan, dependency audit, Compose and diff checks: PASS
• evidence/verifier/strict fallback reviewer: PASS / NONE
• reviewer findings: 0 HIGH, 0 MEDIUM
• reviewed P2 content SHA: a0971c125204e1aa5482ebe612ef75baf2bf21fb
• final PR head: 64aa60472eab042461f3317fe1b84ca8ae427c66
• follow-up 64aa604 replaces the local-only /tmp/directpilot-p2-bin/docker test default with docker from PATH while preserving DIRECTPILOT_DOCKER_BIN
• PR-triggered CI, Security, P1 quality, and P2 PostgreSQL migrations: PASS on the final head

Safety boundary

• no production deploy or migration execution
• no live Yandex/Direct write or provider call
• no real credentials or customer data
• merge remains a separate action