feat(p2p): add Phase 3 dispute system components

- Add DisputeModal.tsx with reason selection, evidence upload, terms acceptance
- Add P2PDispute.tsx page with evidence gallery, status timeline, real-time updates
- Integrate dispute button in P2PTrade.tsx
- Add /p2p/dispute/:disputeId route to App.tsx
- Add P2P test suite with MockStore pattern (32 tests passing)
- Update P2P-BUILDING-PLAN.md with Phase 3 progress (70% complete)
- Fix lint errors in test files and components

web/package.json

@@ -90,6 +90,7 @@
     "@tailwindcss/typography": "^0.5.16",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.0",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^22.5.5",
     "@types/qrcode": "^1.5.6",
     "@types/react": "^18.3.3",