✨ Add skills page with category grouping (Story 2.4)

- Enhance Skill model with getCurrentLevel() and ordered scope
- Update SkillController to group by category with translated labels
- Add level and project_count to SkillResource
- Create skill.ts types (Skill, SkillCategory, SkillsResponse)
- Create useFetchSkills composable
- Create SkillCard component with animated progress bar
- Implement competences.vue with:
  - Responsive grid (2/3/4 columns)
  - Category sections with icons
  - Stagger animations (respects prefers-reduced-motion)
  - Loading/error/empty states
  - Placeholder for vis.js skill tree (Epic 3)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/implementation-artifacts/sprint-status.yaml

@@ -60,7 +60,7 @@ development_status:
   2-1-composant-projectcard: review
   2-2-page-projets-galerie: review
   2-3-page-projet-detail: review
-  2-4-page-competences-affichage-categories: ready-for-dev
+  2-4-page-competences-affichage-categories: review
   2-5-competences-cliquables-projets-lies: ready-for-dev
   2-6-page-temoignages-migrations-bdd: ready-for-dev
   2-7-composant-dialogue-pnj: ready-for-dev