feat: update user-facing 'Simple Mode' terminology to 'App Mode' (#8590)

## Summary
Updates all user-facing instances of 'Simple Mode' / 'Linear Mode' to
'App Mode' as discussed in PR #8562.

## Changes
- Updated command label in `useCoreCommands.ts`
- Updated `src/locales/en/commands.json`
- Updated all 12 locale `main.json` files with:
  - `linearMode.linearMode` → "App Mode" (translated)
  - `linearMode.beta` → "App Mode in Beta - Feedback" (translated)
  - `Toggle Simple Mode` command → `Toggle App Mode` (translated)

## Languages Updated
en, zh, zh-TW, ja, ko, fr, es, pt-BR, ru, tr, ar, fa

## Notes
Internal variable names (`linearMode`, `canvasStore.linearMode`) remain
unchanged to avoid breaking changes.

Fixes #8577

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Style**
* Renamed application terminology from "Simple Mode" to "App Mode" in
user interface labels, mode descriptions, and mode toggle command.
Updates applied consistently across all 12 supported language
translations to ensure consistent terminology throughout the
application.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8590-feat-update-user-facing-Simple-Mode-terminology-to-App-Mode-2fc6d73d36508160a19af70b228b0a7e)
by [Unito](https://www.unito.io)

src/locales/ja/main.json

@@ -1152,11 +1152,11 @@
     "helpFix": "これを修正するのを助ける"
   },
   "linearMode": {
-    "beta": "ベータ版 - フィードバックを送る",
+    "beta": "アプリモード ベータ版 - フィードバックを送る",
     "downloadAll": "すべてダウンロード",
     "dragAndDropImage": "画像をドラッグ＆ドロップ",
     "graphMode": "グラフモード",
-    "linearMode": "シンプルモード",
+    "linearMode": "アプリモード",
     "rerun": "再実行",
     "reuseParameters": "パラメータを再利用",
     "runCount": "実行回数："
@@ -1648,7 +1648,7 @@
     "Toggle Logs Bottom Panel": "ログ下部パネルの切り替え",
     "Toggle Queue Panel V2": "キューパネルV2を切り替え",
     "Toggle Search Box": "検索ボックスの切り替え",
-    "Toggle Simple Mode": "シンプルモードを切り替え",
+    "Toggle App Mode": "アプリモードを切り替え",
     "Toggle Terminal Bottom Panel": "ターミナル下部パネルの切り替え",
     "Toggle Theme (Dark/Light)": "テーマを切り替え（ダーク/ライト）",
     "Toggle View Controls Bottom Panel": "ビューコントロール下部パネルの切り替え",