fix: avoid MySQL thread_meta refresh races and harden roundtable bootstrap

Skip post-commit ORM refresh on threads_meta creates so concurrent MySQL
read/write-split deployments no longer fail with Could not refresh instance;
clean up partial roundtable threads on checkpoint failure, and ship related
position-roundtable/frontend build fixes.

Co-authored-by: Cursor <cursoragent@cursor.com>

.dockerignore

@@ -0,0 +1,35 @@
+# Never send source-control history, local dependencies, runtime state, or
+# credentials to the Docker daemon.  The offline images are built from the
+# repository root by deploy/1panel-offline/Dockerfile.*.
+.git
+.runtime
+.history
+tmp
+dist
+
+# Credentials and environment-specific configuration are supplied at runtime
+# through the offline delivery package, never copied into an image layer.
+**/.env
+**/.env.*
+offline-backend-20260512/backend/.deer-flow
+offline-backend-20260512/backend/logs
+offline-backend-20260512/backend/docker-data
+offline-backend-20260512/backend/dist
+offline-backend-20260512/backend/wheelhouse
+offline-backend-20260512/backend/offline-wheels
+offline-backend-20260512/backend/.venv
+offline-backend-20260512/backend/.pytest_cache
+offline-backend-20260512/backend/.ruff_cache
+
+# Reproducibly install frontend dependencies inside the image instead.
+frontend-web/node_modules
+frontend-web/dist
+frontend-web/.vite
+frontend-web/.offline-pack-build
+frontend-web/.offline-extract-test
+frontend-web/node_modules-offline-*.tar.gz
+
+# Editor and operating-system metadata.
+**/__pycache__
+**/*.py[cod]
+**/.DS_Store