fix(docker,release): multi-stage frontend build, asset distribution, and bump to v2.17.1

[spelech]

Summary

Resolves white-screen error (NS_ERROR_CORRUPTED_CONTENT / disallowed MIME type ("application/json")) on https://contextcortex.wileyriley.com caused by missing frontend assets in the published Docker container.

Root Cause

1. Root .gitignore pattern: .gitignore contained dist/ rather than /dist/, causing git to ignore frontend/dist/assets/ while frontend/dist/index.html was tracked.
2. Single-Stage Docker Build in CI: Dockerfile did not compile the frontend, relying on COPY . .. In GitHub Actions docker-publish.yml, the build-and-push runner checked out git (which lacked assets/), producing container images that had index.html referencing scripts that did not exist in the container.
3. Stale Asset Fallback in main.py: When frontend/dist/index.html was detected without frontend/dist/assets, main.py fell back to www/assets (which contained old August 15 bundle hashes). FastAPI returned 404 JSON for missing assets, causing the browser to reject the scripts as modules.

Key Changes

• Multi-Stage Dockerfile: Built with node:22-alpine frontend build stage running npm ci and npm run build, bundling the resulting distribution into both /app/frontend/dist and /app/www.
• Build Context Optimization (.dockerignore): Excluded .git, .venv, and node_modules, reducing Docker context transfer from 920MB to 6MB.
• Fixed .gitignore: Changed dist/ to /dist/ and ignored docs/.vitepress/dist/.
• Resilient Static Mounting in main.py: Ensures frontend/dist is only selected if both index.html and assets exist together.
• Favicon Routes: Added /favicon.svg and /favicon.ico endpoints and included them in AuthMiddleware public bypass.
• Version Bump: Bumped to v2.17.1 across all manifests and documentation.

Visual Verification

Verification

• Backend Pytest Suite: 548 passing, 2 skipped
• Frontend Vitest Suite: 323 passing
• Release verification engine (scripts/verify_release.py): All 78 markdown links and version consistency checks passed.