fix: unify dialog layout and fix content padding issues

- Fix negative margin overflow in all dialog content areas
- Standardize dialog structure with flex-col layout
- Add consistent py-4 spacing to all content areas
- Ensure proper spacing between header, content, and footer

Affected components:
- AddProviderDialog, EditProviderDialog
- McpFormModal, McpPanel
- UsageScriptModal
- SettingsDialog

All dialogs now follow unified layout pattern:
- DialogContent: flex flex-col max-h-[90vh]
- Content area: flex-1 overflow-y-auto px-6 py-4
- No negative margins that cause content overflow

src/components/providers/forms/CodexCommonConfigModal.tsx

@@ -33,7 +33,10 @@ export const CodexCommonConfigModal: React.FC<CodexCommonConfigModalProps> = ({
 
   return (
     <Dialog open={isOpen} onOpenChange={(open) => !open && onClose()}>
-      <DialogContent zIndex="nested" className="max-w-2xl max-h-[90vh] flex flex-col p-0">
+      <DialogContent
+        zIndex="nested"
+        className="max-w-2xl max-h-[90vh] flex flex-col p-0"
+      >
         <DialogHeader className="px-6 pt-6 pb-0">
           <DialogTitle>{t("codexConfig.editCommonConfigTitle")}</DialogTitle>
         </DialogHeader>