feat: migrate frontend React 18 → Svelte 5 + SvelteKit

Core logic portable (economy, balance, cosmetics, migrateSave) — zero rewrite.
136 tests green, identiques. Backend inchangé.

- Svelte 5 runes stores (game, auth, toast) remplacent Zustand
- SvelteKit adapter-static SPA (dist/ output, fallback index.html)
- Tailwind v4 conservé, design system .gp-* porté
- Transitions natives : slide, fly, scale, fade sur toute l'UI
- Sidebar tabbée (Production/Evolution/Collection) + CollapsiblePanel
- Mobile bottom sheet avec FAB toggle + backdrop blur
- Click particles réactifs Svelte (plus de DOM impératif)
- TadpoleSprite bounce + glow ring au clic
- Guide refait en accordéon, Achievements avec filtres
- a11y : focus-visible, Escape modals, aria-current, aria-labels
- CI/CD adapté (tests + build + rsync)
- Build 504K (vs ~1.2MB React)

.gitea/workflows/deploy.yml

@@ -42,11 +42,16 @@ jobs:
           npm ci
           npm run build
 
+      - name: Run frontend tests
+        working-directory: Frontend
+        run: npx vitest run
+
       - name: Deploy frontend
         if: github.event_name == 'push' && github.ref == 'refs/heads/main'
         run: |
           mkdir -p /var/www/clickerz/frontend/dist
           rsync -a --delete Frontend/dist/ /var/www/clickerz/frontend/dist/
+          echo "✅ Frontend Svelte deployed"
 
       # ── Smoke test ───────────────────────────────────────────────────────────
       - name: Smoke test API