feat: add column pinning (freeze) functionality in Pricing Units tab

- Add Pin Columns button to select columns to freeze
- Implement sticky columns with left positioning for pinned columns
- Support pinning dynamic pricing and container columns
- Add Pin icon indicator on pinned columns
- Include reset and unpin all options in pin panel

src/components/EditPanel.tsx

@@ -195,7 +195,6 @@ export function EditPanel({ row, rowIndex, onSave, onClose, onCaptureState }: Ed
   const executeGenerate = async () => {
     if (!pendingGeminiField) return;
     const field = pendingGeminiField;
-    setPendingGeminiField(null);
     setLoadingField(field);
     setError(null);
 
@@ -283,8 +282,10 @@ export function EditPanel({ row, rowIndex, onSave, onClose, onCaptureState }: Ed
         const textarea = document.getElementById(`field-${field}`);
         if (textarea) textarea.focus();
       }, 100);
+      setPendingGeminiField(null);
     } catch (err: any) {
       setError(err.message || 'An error occurred during generation.');
+      setPendingGeminiField(null); // Close modal on error so error message is visible in panel
     } finally {
       setLoadingField(null);
     }
@@ -489,6 +490,7 @@ export function EditPanel({ row, rowIndex, onSave, onClose, onCaptureState }: Ed
 
         <ConfirmModal 
           isOpen={!!pendingGeminiField}
+          isLoading={loadingField !== null}
           onConfirm={executeGenerate}
           onCancel={() => setPendingGeminiField(null)}
           title="Confirm AI Action"