docs(06.2): capture phase context + fix admin user creation 500

- Phase 6.2 CONTEXT.md: cloud-delete propagation, SHARE-03/05, audit
  log CSV export fix, daily export UI, user handle display
- Fix: admin create_user missing session.flush() before write_audit_log
  caused FK violation on PostgreSQL (silent on SQLite)
- Regression test: test_create_user_writes_audit_log in test_admin_api.py

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

backend/api/admin.py

@@ -244,6 +244,7 @@ async def create_user(
         used_bytes=0,
     )
     session.add(quota)
+    await session.flush()  # persist User + Quota before audit_log FK references them
     # D-13: admin user created event
     _ip = request.headers.get("X-Forwarded-For") or (request.client.host if request.client else None)
     await write_audit_log(