refactor: create shared react-i18next mock to reduce duplication (#29711)

.claude/skills/frontend-testing/CHECKLIST.md

@@ -76,7 +76,7 @@ Use this checklist when generating or reviewing tests for Dify frontend componen
 - [ ] **DO NOT mock base components** (`@/app/components/base/*`)
 - [ ] `jest.clearAllMocks()` in `beforeEach` (not `afterEach`)
 - [ ] Shared mock state reset in `beforeEach`
-- [ ] i18n mock returns keys (not empty strings)
+- [ ] i18n uses shared mock (auto-loaded); only override locally for custom translations
 - [ ] Router mocks match actual Next.js API
 - [ ] Mocks reflect actual component conditional behavior
 - [ ] Only mock: API services, complex context providers, third-party libs

.claude/skills/frontend-testing/SKILL.md

@@ -318,3 +318,4 @@ For more detailed information, refer to:
 - `web/jest.config.ts` - Jest configuration
 - `web/jest.setup.ts` - Test environment setup
 - `web/testing/analyze-component.js` - Component analysis tool
+- `web/__mocks__/react-i18next.ts` - Shared i18n mock (auto-loaded by Jest, no explicit mock needed; override locally only for custom translations)

.claude/skills/frontend-testing/guides/mocking.md

@@ -46,12 +46,22 @@ Only mock these categories:
 
 ## Essential Mocks
 
-### 1. i18n (Always Required)
+### 1. i18n (Auto-loaded via Shared Mock)
+
+A shared mock is available at `web/__mocks__/react-i18next.ts` and is auto-loaded by Jest.
+**No explicit mock needed** for most tests - it returns translation keys as-is.
+
+For tests requiring custom translations, override the mock:
 
 ```typescript
 jest.mock('react-i18next', () => ({
   useTranslation: () => ({
-    t: (key: string) => key,
+    t: (key: string) => {
+      const translations: Record<string, string> = {
+        'my.custom.key': 'Custom translation',
+      }
+      return translations[key] || key
+    },
   }),
 }))
 ```
@@ -313,7 +323,7 @@ Need to use a component in test?
 │  └─ YES → Mock it (next/navigation, external SDKs)
 │
 └─ Is it i18n?
-   └─ YES → Mock to return keys
+   └─ YES → Uses shared mock (auto-loaded). Override only for custom translations
 ```
 
 ## Factory Function Pattern