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/src/components/p2p/TradeModal.tsx

@@ -1,4 +1,5 @@
 import React, { useState } from 'react';
+import { useNavigate } from 'react-router-dom';
 import {
   Dialog,
   DialogContent,
@@ -15,7 +16,7 @@ import { Loader2, AlertTriangle, Clock } from 'lucide-react';
 import { useAuth } from '@/contexts/AuthContext';
 import { usePolkadot } from '@/contexts/PolkadotContext';
 import { toast } from 'sonner';
-import { type P2PFiatOffer } from '@shared/lib/p2p-fiat';
+import { acceptFiatOffer, type P2PFiatOffer } from '@shared/lib/p2p-fiat';
 
 interface TradeModalProps {
   offer: P2PFiatOffer;
@@ -23,6 +24,7 @@ interface TradeModalProps {
 }
 
 export function TradeModal({ offer, onClose }: TradeModalProps) {
+  const navigate = useNavigate();
   const { user } = useAuth();
   const { api, selectedAccount } = usePolkadot();
   const [amount, setAmount] = useState('');
@@ -60,18 +62,18 @@ export function TradeModal({ offer, onClose }: TradeModalProps) {
     setLoading(true);
 
     try {
-      // const _tradeId = await acceptFiatOffer({
-      //   api,
-      //   account: selectedAccount,
-      //   offerId: offer.id,
-      //   amount: cryptoAmount
-      // });
+      const tradeId = await acceptFiatOffer({
+        api,
+        account: selectedAccount,
+        offerId: offer.id,
+        amount: cryptoAmount
+      });
 
       toast.success('Trade initiated! Proceed to payment.');
       onClose();
-      
-      // TODO: Navigate to trade page
-      // navigate(`/p2p/trade/${tradeId}`);
+
+      // Navigate to trade page
+      navigate(`/p2p/trade/${tradeId}`);
     } catch (error) {
       if (import.meta.env.DEV) console.error('Accept offer error:', error);
       // Error toast already shown in acceptFiatOffer