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/hooks/useSettings.ts

@@ -4,10 +4,7 @@ import { toast } from "sonner";
 import { settingsApi, type AppType } from "@/lib/api";
 import { useSettingsQuery, useSaveSettingsMutation } from "@/lib/query";
 import type { Settings } from "@/types";
-import {
-  useSettingsForm,
-  type SettingsFormState,
-} from "./useSettingsForm";
+import { useSettingsForm, type SettingsFormState } from "./useSettingsForm";
 import {
   useDirectorySettings,
   type ResolvedDirectories,