Scope git commit to current diagram + fix complete JSON export/import

- Git commit: "Current diagram only" checkbox stages only that diagram's
  JSON file instead of all diagrams
- JSON export now includes: waypoints, twisted_pair, twist_pitch, shielded,
  show_size_label, bundle_id, bundle_label, sheet_id, sheets, wire_bundles
- JSON import reconstructs sheets and bundles with remapped IDs so restored
  diagrams are exact copies

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

backend/app/routers/export.py

@@ -283,13 +283,25 @@ def export_json(diagram_id: int, db: Session = Depends(get_db)):
     if not diagram:
         raise HTTPException(status_code=404, detail="Diagram not found")
 
+    # Build bundle id→label map for wire export
+    bundle_label = {b.id: b.label for b in diagram.wire_bundles}
+
     data = {
         "id": diagram.id,
         "name": diagram.name,
         "description": diagram.description,
+        "sheets": [
+            {"id": s.id, "name": s.name, "position": s.position}
+            for s in diagram.sheets
+        ],
+        "wire_bundles": [
+            {"id": b.id, "label": b.label, "jacket_color": b.jacket_color}
+            for b in diagram.wire_bundles
+        ],
         "devices": [
             {
-                "id": d.id, "device_type": d.device_type, "label": d.label,
+                "id": d.id, "sheet_id": d.sheet_id,
+                "device_type": d.device_type, "label": d.label,
                 "reference": d.reference, "x": d.x, "y": d.y,
                 "width": d.width, "height": d.height,
                 "properties": d.properties, "pins": d.pins,
@@ -298,12 +310,19 @@ def export_json(diagram_id: int, db: Session = Depends(get_db)):
         ],
         "wires": [
             {
-                "id": w.id, "label": w.label,
+                "id": w.id, "sheet_id": w.sheet_id, "label": w.label,
                 "from_device_id": w.from_device_id, "from_pin": w.from_pin,
                 "to_device_id": w.to_device_id, "to_pin": w.to_pin,
                 "color_primary": w.color_primary, "color_stripe": w.color_stripe,
                 "gauge": w.gauge, "length": w.length, "length_unit": w.length_unit,
                 "notes": w.notes,
+                "waypoints": w.waypoints or [],
+                "twisted_pair": bool(w.twisted_pair),
+                "twist_pitch": w.twist_pitch,
+                "shielded": bool(w.shielded),
+                "show_size_label": bool(w.show_size_label),
+                "bundle_id": w.bundle_id,
+                "bundle_label": bundle_label.get(w.bundle_id),
             }
             for w in diagram.wires
         ],