Security hardening: fix command injection, path traversal, unauthenticated reset

Remove open dependency, add LICENSE, SECURITY.md, fix README

Fix README images for npm: use absolute GitHub URLs

Fix npx diffback-review: add bin alias matching package name

Bump version to 1.3.0

Theme selector, file stats, filters, inline comments, tests, responsive UI, README gallery

Add syntax highlighting with Solarized Dark colors

Rename npm package to diffback-review and update docs

Add goodbye screen with countdown on finish review

Upgrade to Node 24 LTS and actions v5

Target Node 22 and ES2024

Fix CI: add node types to tsconfig, single Node 22 build

Add CI workflow

Initial release: diffback