feat(12-02): FieldPlacer onFieldsChanged callback prop after every persistFields call

- Add onFieldsChanged?: () => void to FieldPlacerProps interface
- Destructure onFieldsChanged in function signature
- Call onFieldsChanged?.() after persistFields in handleDragEnd (new field drop)
- Call onFieldsChanged?.() after persistFields in handleZonePointerUp move case
- Call onFieldsChanged?.() after persistFields in handleZonePointerUp resize case
- Call onFieldsChanged?.() after persistFields in delete button onClick
- Add onFieldsChanged to useCallback dependency arrays (handleDragEnd, handleZonePointerUp)

teressa-copeland-homes/src/app/portal/(protected)/documents/[docId]/_components/FieldPlacer.tsx

@@ -155,9 +155,10 @@ interface FieldPlacerProps {
   currentPage: number;
   children: React.ReactNode;
   readOnly?: boolean;
+  onFieldsChanged?: () => void;
 }
 
-export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly = false }: FieldPlacerProps) {
+export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly = false, onFieldsChanged }: FieldPlacerProps) {
   const [fields, setFields] = useState<SignatureFieldData[]>([]);
   const [isDraggingToken, setIsDraggingToken] = useState<string | null>(null);
   const containerRef = useRef<HTMLDivElement | null>(null);
@@ -294,8 +295,9 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly =
       const next = [...fields, newField];
       setFields(next);
       persistFields(docId, next);
+      onFieldsChanged?.();
     },
-    [fields, pageInfo, currentPage, docId, readOnly],
+    [fields, pageInfo, currentPage, docId, readOnly, onFieldsChanged],
   );
 
   // --- Move / Resize pointer handlers (event delegation on DroppableZone) ---
@@ -477,6 +479,7 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly =
       });
       setFields(next);
       persistFields(docId, next);
+      onFieldsChanged?.();
     } else if (drag.type === 'resize') {
       const corner = drag.corner ?? 'se';
       const startW = drag.startFieldW ?? 144;
@@ -543,8 +546,9 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly =
       });
       setFields(next);
       persistFields(docId, next);
+      onFieldsChanged?.();
     }
-  }, [docId]);
+  }, [docId, onFieldsChanged]);
 
   // Render placed fields for the current page
   // Uses pageInfo.width/height (not getBoundingClientRect) for consistent coordinate math
@@ -653,6 +657,7 @@ export function FieldPlacer({ docId, pageInfo, currentPage, children, readOnly =
                   const next = fields.filter((f) => f.id !== field.id);
                   setFields(next);
                   persistFields(docId, next);
+                  onFieldsChanged?.();
                 }}
                 onPointerDown={(e) => {
                   // Prevent dnd-kit sensors and move handler from capturing this pointer event