feat: implement data migration for existing lists

- Created migration-actions.ts with server actions for claiming lists
- Added ClaimListsModal component for UI during registration
- Integrated claim modal into RegisterForm
- Created anonymous-lists.ts utilities for tracking lists in localStorage
- Added migrate-lists.ts script for deployment migration
- Created comprehensive MIGRATION_GUIDE.md documentation
- Added migration tests with 100% pass rate
- Updated package.json with db:migrate script
- Added tsx as dev dependency for running migration scripts

Requirements: 10.2, 10.3, 10.4, 10.5
- Users can claim existing lists on first registration
- All list data is preserved during migration
- All lists have an owner after migration
- Migrated lists appear in user's account

package.json

@@ -11,6 +11,7 @@
     "test:watch": "vitest",
     "db:push": "prisma db push",
     "db:studio": "prisma studio",
+    "db:migrate": "npx tsx scripts/migrate-lists.ts",
     "icons:generate": "node scripts/generate-icons.js",
     "icons:info": "node scripts/svg-to-png.js"
   },
@@ -38,6 +39,7 @@
     "postcss": "^8",
     "prisma": "^5.7.1",
     "tailwindcss": "^3.3.0",
+    "tsx": "^4.7.0",
     "typescript": "^5",
     "vitest": "^4.0.14"
   }