chore: commit pending phase-3 work and add TEST_ACCOUNTS.md

Includes planning artifacts (03-CONTEXT, 03-DISCUSSION-LOG, 03-02-SUMMARY),
integration test script, MinIO/auth/docker fixes, and local dev account reference.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/services/auth.py

@@ -423,6 +423,7 @@ async def bootstrap_admin(session: AsyncSession) -> None:
         used_bytes=0,
     )
     session.add(admin_user)
+    await session.flush()  # persist User first so Quota FK is satisfied
     session.add(quota)
     await session.commit()
     logger.info("Admin account bootstrapped for %s", settings.admin_email)