Update wiring diagram maker: formboard router + frontend

Backend formboard router and frontend (canvas, formboard, connector library,
app/api, index/css) updates. Ignore *.log.

frontend/index.html

@@ -230,6 +230,9 @@
             <button id="prop-add-pin" style="flex:1;font-size:11px;padding:3px 6px">+ Add Pin</button>
             <button id="prop-save-connector" class="btn-primary" style="flex:1;font-size:11px;padding:3px 6px">⬆ Save to Library</button>
           </div>
+          <div style="margin-top:4px">
+            <button id="prop-pinout-btn" style="display:none;width:100%;font-size:11px;padding:3px 6px">⊙ View Pinout</button>
+          </div>
         </div>
       </div>
 
@@ -459,6 +462,39 @@
   </div>
 </div>
 
+<!-- ── Pinout Modal ───────────────────────────────────────────────────────────── -->
+<div id="pinout-modal" style="display:none">
+  <div class="modal-box" style="min-width:580px;max-width:700px">
+    <div class="modal-header">
+      <h3 id="pinout-modal-title">Connector Pinout</h3>
+      <span id="pinout-info" style="font-size:11px;color:#888;margin-left:10px"></span>
+    </div>
+    <div class="modal-body" style="flex-direction:row;align-items:flex-start;padding:14px;gap:16px">
+      <div id="pinout-svg-container" style="flex-shrink:0"></div>
+      <div style="flex:1;display:flex;flex-direction:column;gap:6px;min-width:0">
+        <div style="font-size:11px;color:#8899cc;font-weight:bold;padding-bottom:2px;border-bottom:1px solid #2a2a4a">Pin Assignments</div>
+        <div id="pinout-table-container" style="overflow-y:auto;max-height:260px">
+          <table id="pinout-table" style="width:100%;border-collapse:collapse;font-size:11px;font-family:monospace">
+            <thead>
+              <tr style="color:#666688;text-align:left">
+                <th style="padding:3px 6px;width:36px">#</th>
+                <th style="padding:3px 6px">Note / Connection</th>
+              </tr>
+            </thead>
+            <tbody id="pinout-table-body"></tbody>
+          </table>
+        </div>
+      </div>
+    </div>
+    <div class="modal-footer">
+      <button id="pinout-print-btn">🖨 Print</button>
+      <button id="pinout-copy-btn">⎘ Copy Table</button>
+      <div style="flex:1"></div>
+      <button id="pinout-close" class="btn-primary">Close</button>
+    </div>
+  </div>
+</div>
+
 <!-- ── Context Menu ──────────────────────────────────────────────────────────── -->
 <div id="ctx-menu">
   <!-- populated dynamically by app.js -->