v0.3.0 — GnUserCard, NavigationShell footer slot, Vue demo partials ...

Features:
- Add GnUserCard Vue component with compact and full variants
- Add GnNavigationShell #footer slot for custom footer content
- Add profile footer demo in navigation-shell section
- Split demo/vue.html into 27 partials under demo/partials/vue/
- Fix toast open animation (nextTick + requestAnimationFrame pattern)

Style:
- Add .user-card and .user-card-compact to _cards.scss
- Add .profile-identity to _navigation-shell.scss

Docs:
- Add demo synchronization rules to CLAUDE.md

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Add GnLoginCard component for standardized login forms ...

- Create GnLoginCard Vue adapter component with username/password
  fields, optional remember-me checkbox, submit button, and
  forgot-password / sign-up links.
- Add `.login-card` styles in _cards.scss with centered header,
  full-width submit button, and spaced link row.
- Register GnLoginCard in plugin and index exports.
- Add login-card demo block to demo/partials/cards.html.
- Update CLAUDE.md, README, and Vue docs with component entry.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>