Add Ledger setup guide and update dashboard

- Complete step-by-step Ledger setup guide
- Requirements checklist
- Browser compatibility info
- Troubleshooting section
- Updated dashboard with Ledger card
- Direct access to Ledger app

Guide covers:
- Hardware preparation
- USB-C connection
- Browser support settings
- WebUSB permissions
- Connection verification
- Feature usage
- Common issues

🤖 Generated with Claude Code

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

dashboard.html

@@ -237,6 +237,18 @@
         </ul>
       </div>
 
+      <div class="app-card" onclick="window.location.href='/ledger.html'" style="border-color: #7700FF;">
+        <h2>🔐 Ledger Hardware</h2>
+        <span class="status">READY</span>
+        <p>Secure hardware wallet via USB-C</p>
+        <ul class="features">
+          <li>✓ WebUSB connection</li>
+          <li>✓ Multi-account (BTC/ETH/SOL)</li>
+          <li>✓ Transaction signing</li>
+          <li>✓ Address verification</li>
+        </ul>
+      </div>
+
       <div class="app-card" onclick="window.location.href='/integrations.html'">
         <h2>🔗 Integrations</h2>
         <span class="status">LIVE</span>