feat(frontend): Integrate backend stats, duplicate & export

Frontend Integration - FASE 1 Completion:
- Dashboard now fetches real project stats from API (/stats endpoint)
- ProjectCard adds duplicate and export actions with toast notifications
- StatsOverview displays real-time data from backend
- Fixed navigation for advanced tools (QA, Marketing, Print, Scientific)
- Added use-toast hook for UI notifications
- Updated translations for landing page

Changes:
- src/app/[locale]/dashboard/page.tsx: Stats integration, tools navigation fix
- src/components/dashboard/ProjectCard.tsx: Duplicate & export actions
- src/components/dashboard/StatsOverview.tsx: Real API data consumption
- src/hooks/use-toast.ts: Toast notification system
- messages/en.json: Added landing.socialProof section
- src/types/project.ts: Updated ProjectStats interface

Backend Ready:
- ✅ GET /api/v1/projects/stats
- ✅ POST /api/v1/projects/:id/duplicate
- ✅ GET /api/v1/projects/:id/export

Next: Production deployment & testing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: JuanCS-Dev

web/messages/en.json

@@ -126,5 +126,11 @@
     "perMonth": "/month",
     "features": "Features included",
     "allFeatures": "All features"
+  },
+  "landing": {
+    "socialProof": {
+      "title": "Trusted by Writers",
+      "subtitle": "Join thousands of authors creating professional books"
+    }
   }
 }