Fix: checkbox text overflow + center share link section

- Removed padding-top:20px and white-space:nowrap from checkbox-group
  labels so long text wraps instead of overflowing
- Wrapped share link/QR section in centered 520px max-width container
  so it doesn't span the entire grid width

index.html

@@ -147,7 +147,7 @@
     display: flex;
     align-items: center;
     gap: 8px;
-    padding-top: 20px;
+    padding: 0;
   }
   .checkbox-group label {
     font-size: 0.82rem;
@@ -155,7 +155,7 @@
     text-transform: none;
     letter-spacing: 0;
     color: var(--text);
-    white-space: nowrap;
+    white-space: normal;
   }
   .checkbox-group input[type="checkbox"] {
     width: 16px;
@@ -523,6 +523,7 @@
 
   <div class="control-group" style="grid-column: 1 / -1;">
     <label>Share this link <span style="font-weight:400;color:var(--text-muted);text-transform:none;letter-spacing:0;font-size:0.68rem;">(sends the plan as-is)</span></label>
+    <div style="max-width:520px;width:100%;margin:0 auto;">
       <div class="shared-link-row">
         <input type="text" id="sharedLink" readonly>
         <button class="copy-sm-btn" id="copyLinkBtn" onclick="copySharedLink()">📄 Copy</button>
@@ -533,6 +534,7 @@
         <div style="font-size:12px;color:var(--text-secondary);margin-top:6px;">📱 Scan to open calculator</div>
       </div>
     </div>
+  </div>
 </div>
 
 <div id="shareablePlan" class="plan-section">