v0.6.3: Docker production builds, image publish pipeline, Python 3.14 fixes

v0.6.3: Docker production builds, image publish pipeline, Python 3.14 fixes

1. All 3 frontend Dockerfiles rewritten as multi-stage builds (Node builder + nginx:stable-alpine serve); each UI served at /ui/react/, /ui/vue/, /ui/angular/ with SPA fallback, gzip, and immutable asset caching
2. Added nginx.conf and .dockerignore for each frontend
3. Backend Dockerfile updated: ARG EXTRAS build argument (default langchain,langchain-extras,rdf,observability) with --override extras-overrides.txt to suppress transitive downgrades
4. Added flexible-graphrag/.dockerignore (excludes .env, venvs, local DBs, uploads, logs)
5. Added .github/workflows/docker-publish.yml: builds 4 images in parallel on v* tag; pushes to docker.io/integratedsemantics/ and ghcr.io/stevereiner/ with semver + latest tags; multi-platform linux/amd64 + linux/arm64
6. docker/includes/app-stack.yaml: added image: integratedsemantics/:${FLEXIBLE_GRAPHRAG_VERSION:-latest} to all 4 services alongside build: contexts
7. docker/nginx/nginx.conf: Angular proxy simplified to direct proxy_pass (removed rewrite + sub_filter); all 3 UIs now use identical proxy pattern
8. main.py Python 3.14 patches: CancelScope rewritten for anyio slots; AsyncShieldCancellation patches httpcore cached references; _patch_ssl_context() fixes Windows CA/VERIFY_X509_STRICT APIConnectionError
9. docker/docker-env-sample.txt and docker.env: added ENABLE_OBSERVABILITY=false override to suppress OTLP export errors when no collector is running; added commented OTEL_EXPORTER_OTLP_ENDPOINT option
10. pyproject.toml versions bumped to 0.6.3
11. Fix frontend package names/versions: rename cmis→flexible-graphrag in Vue/Angular package-lock.json, bump all three frontends to v0.6.3, add React and Vue SVG favicons