feat: add stable version management for footer display

[JeevanMahesha]

Description

The docs footer displayed the monorepo's working package.json version directly (require('@/package.json').version), which currently holds an in-progress pre-release identifier like 2.0.0-rc.0. Since the docs site is deployed continuously from main, this meant every page footer showed an unreleased RC version instead of the actual latest stable release published on npm.

Before: footer shows Optimus UI 2.0.0-rc.0
After: footer shows Optimus UI 1.0.1 (the real latest dist-tag for @openng/optimus-ui)

Fix: added a build step (scripts/build-stable-version.mjs) that queries the npm registry for @openng/optimus-ui's latest dist-tag and writes it to assets/data/stable-version.json, which the footer now imports instead of reading package.json directly. Falls back to the local package.json version (stripped of any pre-release suffix) if the registry is unreachable, so the build never fails outright. Wired into the existing build:docs pipeline alongside the other generated-asset scripts (routes, sitemap, etc.).

Related issues

Fixes #1445

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes the public API)
• Documentation only
• Refactor, test, or chore (no user-facing change)

Breaking changes

None.

Test plan

• node apps/docs/scripts/build-stable-version.mjs — confirmed it generates 1.0.1 (npm's current latest dist-tag), not the working 2.0.0-rc.0
• npx tsc -p apps/docs/tsconfig.json --noEmit — no type errors from the new JSON import
• npm run build
• npm test
• npm run lint
• Verified footer renders "Optimus UI 1.0.1" instead of "Optimus UI 2.0.0-rc.0"

Checklist

• Issue discussed or bug clearly described (link issue when applicable)
• Tests added or updated for behavioral changes
• Documentation updated (README, JSDoc, migration notes as needed)
• Public API changes documented; breaking changes called out
• CHANGELOG updated (if the repository maintains one and the change is user-facing)
• Commit messages follow Conventional Commits
• I agree to follow the OpenNG Foundation Code of Conduct

Additional context

The generated assets/data/stable-version.json is committed to the repo, following the same convention as other build-generated docs assets (public/sitemap.xml, router/routes.txt) — it gets refreshed on the next build:docs run whenever a new stable version is published to npm.