Add views, import/duplicate, DRC, jumps toggle, multi-wire select, auto-route, delete view tabs

- Roadmap #22: File→Import JSON to restore a diagram (drag-drop or file picker)
- Roadmap #23: Duplicate diagram from diagram list
- Roadmap #24: DRC panel with collapsible categories (unconnected pins, dup refs, no length, no P/N)
- Multi-view tabs: named views per diagram with independent device/wire layouts; snapshot-on-entry prevents bleed
- Keyboard arrow nudge for selected device(s)
- Undo for move, duplicate, label/property changes
- Wire jump arcs toggle (⌒ Jumps button in toolbar)
- Shift+click multi-wire selection; right-click bulk clear waypoints or auto-route
- Auto-route: obstacle-avoiding ortho routing for single or bulk selected wires
- Delete view tab with × button; right-click context menu for rename/delete

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

frontend/index.html

@@ -28,6 +28,7 @@
       <button id="btn-route-curved" class="route-btn"        title="Curved (smooth bezier) routing">∿ Curved</button>
       <div class="sep"></div>
       <!-- Actions -->
+      <button id="btn-jumps"     title="Toggle wire jump arcs at crossings" class="jumps-btn active">⌒ Jumps</button>
       <button id="btn-snap"      title="Toggle grid snap (G)" class="snap-btn">⊹ Snap</button>
       <button id="btn-harness"   title="Toggle harness view (H)">⌇ Harness</button>
       <button id="btn-fit"       title="Fit canvas to devices (F)">⊞ Fit</button>
@@ -37,10 +38,12 @@
     </div>
 
     <div class="toolbar-right">
+      <button id="btn-drc" title="Run design-rule check">⚠ DRC</button>
       <div id="saved-indicator">✓ Saved</div>
       <div class="export-wrap">
         <button id="export-toggle">Export ▾</button>
         <div id="export-menu">
+          <button id="btn-import">📂 Import JSON</button>
           <button id="btn-bom">📋 BOM (CSV)</button>
           <button id="btn-assembly">📄 Assembly (TXT)</button>
           <button id="btn-json">{ } JSON</button>
@@ -49,6 +52,7 @@
         </div>
       </div>
     </div>
+    <input id="import-file-input" type="file" accept=".json" style="display:none">
   </header>
 
   <!-- ── Mode bar ─────────────────────────────────────────────────────────── -->
@@ -96,6 +100,11 @@
 
     <!-- Canvas -->
     <main id="canvas-area">
+      <!-- View tab bar -->
+      <div id="view-tab-bar" style="display:none">
+        <button class="view-tab active" data-view-id="main">Main</button>
+        <button id="btn-add-view" title="Add view">+</button>
+      </div>
       <div id="canvas-container"></div>
       <div id="canvas-placeholder">
         <div class="placeholder-content">
@@ -395,6 +404,21 @@
   <!-- populated dynamically by app.js -->
 </div>
 
+<!-- ── DRC Modal ──────────────────────────────────────────────────────────────── -->
+<div id="drc-modal" style="display:none">
+  <div class="modal-box" style="min-width:480px;max-width:640px">
+    <div class="modal-header">
+      <h3>Design Rule Check</h3>
+    </div>
+    <div class="modal-body" id="drc-results" style="max-height:400px;overflow-y:auto;font-size:12px;padding:10px;gap:6px">
+    </div>
+    <div class="modal-footer">
+      <div style="flex:1"></div>
+      <button id="drc-close" class="btn-primary">Close</button>
+    </div>
+  </div>
+</div>
+
 <script src="https://unpkg.com/konva@9/konva.min.js"></script>
 <script src="/js/api.js"></script>
 <script src="/js/deviceTypes.js"></script>