Add type parameters to vi.fn() mocks for oxlint 1.60 vitest rule

oxlint 1.60 enables vitest/require-mock-type-parameters by default,
which requires explicit type parameters on all vi.fn() calls.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/views/__tests__/EventStubView.spec.ts

@@ -46,7 +46,7 @@ describe('EventStubView', () => {
   })
 
   it('copies link to clipboard and shows confirmation', async () => {
-    const writeTextMock = vi.fn().mockResolvedValue(undefined)
+    const writeTextMock = vi.fn<(text: string) => Promise<void>>().mockResolvedValue(undefined)
     Object.assign(navigator, {
       clipboard: { writeText: writeTextMock },
     })
@@ -63,7 +63,7 @@ describe('EventStubView', () => {
 
   it('shows failure message when clipboard is unavailable', async () => {
     Object.assign(navigator, {
-      clipboard: { writeText: vi.fn().mockRejectedValue(new Error('Not allowed')) },
+      clipboard: { writeText: vi.fn<(text: string) => Promise<void>>().mockRejectedValue(new Error('Not allowed')) },
     })
 
     const wrapper = await mountWithToken('fail-test')