Add digital e-signature waiver + update How It Works to 5 steps

- waiver.php: full rental agreement with canvas e-signature pad, 6 required
  checkboxes, typed name field; stores sig image + IP + timestamp in DB;
  emails signed confirmation to customer and admin
- bookings table: add waiver_signed, waiver_signed_at, waiver_ip, waiver_name,
  waiver_sig columns
- contact.php: confirmation email now includes Sign Rental Agreement button/link
- admin/index.php: Waiver column shows Signed (date) or Pending + Send Link
- index.html: How It Works expanded to 5 steps (added Get Approved + Sign Waiver
  before Hit the Road); insurance updated to Proof of insurance required; FAQ
  and JSON-LD updated to match

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin/index.php

@@ -195,7 +195,7 @@ textarea.notes-ta{width:100%;font-size:.8rem;border:1px solid #e5e7eb;border-rad
       <thead>
         <tr>
           <th>Ref</th><th>Customer</th><th>Package</th><th>Date</th>
-          <th>Amount</th><th>Status</th><th>Admin Notes</th><th>Received</th>
+          <th>Amount</th><th>Status</th><th>Waiver</th><th>Admin Notes</th><th>Received</th>
         </tr>
       </thead>
       <tbody>
@@ -225,6 +225,16 @@ textarea.notes-ta{width:100%;font-size:.8rem;border:1px solid #e5e7eb;border-rad
               <?php endforeach; ?>
             </select>
           </td>
+          <td>
+            <?php if ($b['waiver_signed']): ?>
+              <span class="badge" style="background:#dcfce7;color:#14532d">&#10003; Signed</span>
+              <br><span style="font-size:.72rem;color:#9ca3af"><?= date('M j g:ia', strtotime($b['waiver_signed_at'])) ?></span>
+            <?php else: ?>
+              <a href="https://parkerslingshotrentals.com/waiver.php?ref=<?= urlencode($b['booking_ref']) ?>" target="_blank"
+                 style="font-size:.78rem;color:#f97316;text-decoration:none">Send Link &#8599;</a>
+              <br><span class="badge" style="background:#fef3c7;color:#92400e;margin-top:.25rem">Pending</span>
+            <?php endif; ?>
+          </td>
           <td>
             <textarea class="notes-ta" data-id="<?= $b['id'] ?>"><?= htmlspecialchars($b['admin_notes'] ?? '') ?></textarea>
             <button class="save-btn" onclick="saveNotes(this)">Save</button>