Modernize vulnerable dependency families

[ShukantPal]

Summary

• Modernize the Babel 7, nanoid, lodash, markdown-it, Rollup 2, webpack 5, PostCSS/SVGO dependency families and regenerate the Rush pnpm lockfile.
• Replace obsolete extract-loader/file-loader stylesheet handling with mini-css-extract-plugin, removing the critical Babel 6 traversal and vulnerable loader-utils chains.
• Replace stale registry-only @webdoc/parser test usage with the maintained local parser packages; remove its obsolete standalone lockfile.

Validation

• rush check
• rush build
• rush lint
• rush flow
• rush unit-test

Stack order

This is stack item 2/3. It targets master, should merge after the CI-baseline PR (1/3), and before the release-discipline PR (3/3).

Deliberate limits

• Rollup remains on the latest v2 patch (2.80.0); Rollup 4 requires Node 18 while this repository still declares Node 12/14/16 support.
• Babel remains on v7 for the same compatibility reason.
• taffydb 2.7.3 has no patched upstream release; its remediation needs a separate API replacement migration rather than an unsafe version bump.