✨ Add project detail page with prev/next navigation (Story 2.3)

- Enhance ProjectController show() with prev/next navigation data
- Create useFetchProject composable with ProjectNavigation type
- Implement [slug].vue with full project details:
  - Hero image, title with featured badge, formatted date
  - Description, external links (site/GitHub)
  - Skills grid with level progression (before → after)
  - Prev/next navigation with project titles
  - 404 state with spider narrator
- Add dynamic SEO meta tags with og:image from project
- Responsive design: stacked mobile, grid desktop

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

frontend/i18n/en.json

@@ -82,7 +82,17 @@
     "discover": "Discover",
     "no_projects": "No projects yet",
     "load_error": "Unable to load projects...",
-    "view_all": "View all projects"
+    "view_all": "View all projects",
+    "not_found": "Project not found",
+    "not_found_description": "This project doesn't exist or has been removed.",
+    "back_to_gallery": "Back to gallery",
+    "completed_on": "Completed on",
+    "visit_site": "Visit site",
+    "view_code": "View code",
+    "skills_used": "Skills used",
+    "skill_level": "Level",
+    "previous": "Previous project",
+    "next": "Next project"
   },
   "pages": {
     "projects": {