feat: add setMany to settingStore for batch setting updates (#8767)

## Summary
- Adds `setMany()` method to `settingStore` for updating multiple
settings in a single API call via the existing `storeSettings` endpoint
- Extracts shared setting-apply logic (`applySettingLocally`) to reduce
duplication between `set()` and `setMany()`
- Migrates all call sites where multiple settings were updated
sequentially to use `setMany()`

## Call sites updated
- `releaseStore.ts` — `handleSkipRelease`, `handleShowChangelog`,
`handleWhatsNewSeen` (3 settings each)
- `keybindingService.ts` — `persistUserKeybindings` (2 settings)
- `coreSettings.ts` — `NavigationMode.onChange` (2 settings)

## Test plan
- [x] Unit tests for `setMany` (batch update, skip unchanged, no-op when
unchanged)
- [x] Updated `releaseStore.test.ts` assertions to verify `setMany`
usage
- [x] Updated `useCoreCommands.test.ts` mock to include `setMany`
- [x] All existing tests pass
- [x] `pnpm typecheck`, `pnpm lint`, `pnpm format` pass

Fixes #1079

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8767-feat-add-setMany-to-settingStore-for-batch-setting-updates-3036d73d36508161b8b6d298e1be1b7a)
by [Unito](https://www.unito.io)

src/scripts/api.ts

@@ -1047,7 +1047,7 @@ export class ComfyApi extends EventTarget {
   /**
    * Stores a dictionary of settings for the current user
    */
-  async storeSettings(settings: Settings) {
+  async storeSettings(settings: Partial<Settings>) {
     return this.fetchApi(`/settings`, {
       method: 'POST',
       body: JSON.stringify(settings)