Implement watch-event feature (017) with bookmark in RsvpBar

Add client-side watch/bookmark functionality: users can save events to
localStorage without RSVPing via a bookmark button next to the "I'm attending"
CTA. Watched events appear in the event list with a "Watching" label.
Bookmark is only visible for visitors (not attendees or organizers).

Includes spec, plan, research, tasks, unit tests, and E2E tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -14,6 +14,9 @@ vi.mock('@/api/client', () => ({
 const mockSaveRsvp = vi.fn()
 const mockGetRsvp = vi.fn()
 const mockGetOrganizerToken = vi.fn()
+const mockSaveWatch = vi.fn()
+const mockIsStored = vi.fn()
+const mockRemoveEvent = vi.fn()
 
 vi.mock('@/composables/useEventStorage', () => ({
   useEventStorage: vi.fn(() => ({
@@ -22,7 +25,10 @@ vi.mock('@/composables/useEventStorage', () => ({
     getOrganizerToken: mockGetOrganizerToken,
     saveRsvp: mockSaveRsvp,
     getRsvp: mockGetRsvp,
-    removeEvent: vi.fn(),
+    removeRsvp: vi.fn(),
+    saveWatch: mockSaveWatch,
+    isStored: mockIsStored,
+    removeEvent: mockRemoveEvent,
   })),
 }))
 
@@ -68,6 +74,9 @@ beforeEach(() => {
   vi.restoreAllMocks()
   mockGetRsvp.mockReturnValue(undefined)
   mockGetOrganizerToken.mockReturnValue(undefined)
+  mockIsStored.mockReturnValue(false)
+  mockSaveWatch.mockClear()
+  mockRemoveEvent.mockClear()
 })
 
 describe('EventDetailView', () => {
@@ -366,4 +375,89 @@ describe('EventDetailView', () => {
     expect(document.body.textContent).toContain('Could not submit RSVP. Please try again.')
     wrapper.unmount()
   })
+
+  // Bookmark — T007: bookmark state is passed to RsvpBar via props
+  it('passes bookmarked=false to RsvpBar when event is not in storage', async () => {
+    mockIsStored.mockReturnValue(false)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    expect(rsvpBar.props('bookmarked')).toBe(false)
+    wrapper.unmount()
+  })
+
+  it('passes bookmarked=true to RsvpBar when event is in storage', async () => {
+    mockIsStored.mockReturnValue(true)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    expect(rsvpBar.props('bookmarked')).toBe(true)
+    wrapper.unmount()
+  })
+
+  it('bookmark event emitted from RsvpBar calls saveWatch', async () => {
+    mockIsStored.mockReturnValue(false)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    rsvpBar.vm.$emit('bookmark')
+    await flushPromises()
+
+    expect(mockSaveWatch).toHaveBeenCalledWith('test-token', 'Summer BBQ', '2026-03-15T20:00:00+01:00')
+    wrapper.unmount()
+  })
+
+  it('bookmark event emitted from RsvpBar calls removeEvent when user is watcher', async () => {
+    mockIsStored.mockReturnValue(true)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    rsvpBar.vm.$emit('bookmark')
+    await flushPromises()
+
+    expect(mockRemoveEvent).toHaveBeenCalledWith('test-token')
+    wrapper.unmount()
+  })
+
+  it('bookmark event ignored when user is attendee', async () => {
+    mockGetRsvp.mockReturnValue({ rsvpToken: 'rsvp-1', rsvpName: 'Max' })
+    mockIsStored.mockReturnValue(true)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    rsvpBar.vm.$emit('bookmark')
+    await flushPromises()
+
+    expect(mockRemoveEvent).not.toHaveBeenCalled()
+    expect(mockSaveWatch).not.toHaveBeenCalled()
+    wrapper.unmount()
+  })
+
+  it('passes bookmarked=true to RsvpBar after removeRsvp (event still in storage)', async () => {
+    mockIsStored.mockReturnValue(true)
+    mockGetRsvp.mockReturnValue(undefined)
+    mockLoadedEvent()
+
+    const wrapper = await mountWithToken()
+    await flushPromises()
+
+    const rsvpBar = wrapper.findComponent({ name: 'RsvpBar' })
+    expect(rsvpBar.props('bookmarked')).toBe(true)
+    wrapper.unmount()
+  })
 })