feat(05-07): cloud connections Pinia store + API client functions

- Create useCloudConnectionsStore with connections/loading/error refs
- fetchConnections, disconnect(id), disconnectAll() actions
- Append listCloudConnections, disconnectCloud, connectWebDav, updateDefaultStorage to api/client.js
- Add vitest test script to package.json
- 4 unit tests passing (W4 — CLAUDE.md)

frontend/src/stores/__tests__/cloudConnections.test.js

@@ -0,0 +1,59 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { setActivePinia, createPinia } from 'pinia'
+
+// Mock api/client.js — no real HTTP calls in unit tests (CLAUDE.md W4)
+vi.mock('../../api/client.js', () => ({
+  listCloudConnections: vi.fn(),
+  disconnectCloud: vi.fn(),
+  connectWebDav: vi.fn(),
+  updateDefaultStorage: vi.fn(),
+}))
+
+import { useCloudConnectionsStore } from '../cloudConnections.js'
+import * as api from '../../api/client.js'
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+  vi.clearAllMocks()
+})
+
+describe('useCloudConnectionsStore', () => {
+  it('fetchConnections sets connections from API response', async () => {
+    api.listCloudConnections.mockResolvedValue({
+      items: [{ id: '1', provider: 'google_drive', status: 'ACTIVE' }],
+    })
+    const store = useCloudConnectionsStore()
+    await store.fetchConnections()
+    expect(store.connections).toHaveLength(1)
+    expect(store.connections[0].provider).toBe('google_drive')
+    expect(store.loading).toBe(false)
+  })
+
+  it('fetchConnections sets error on API failure', async () => {
+    api.listCloudConnections.mockRejectedValue(new Error('Network error'))
+    const store = useCloudConnectionsStore()
+    await store.fetchConnections()
+    expect(store.error).toBeTruthy()
+    expect(store.connections).toHaveLength(0)
+  })
+
+  it('disconnect removes connection from state after API call', async () => {
+    api.disconnectCloud.mockResolvedValue(null)
+    const store = useCloudConnectionsStore()
+    store.connections = [{ id: 'conn-1', provider: 'google_drive', status: 'ACTIVE' }]
+    await store.disconnect('conn-1')
+    expect(store.connections).toHaveLength(0)
+    expect(api.disconnectCloud).toHaveBeenCalledWith('conn-1')
+  })
+
+  it('disconnectAll clears all connections', async () => {
+    api.disconnectCloud.mockResolvedValue(null)
+    const store = useCloudConnectionsStore()
+    store.connections = [
+      { id: 'a', provider: 'google_drive', status: 'ACTIVE' },
+      { id: 'b', provider: 'onedrive', status: 'ACTIVE' },
+    ]
+    await store.disconnectAll()
+    expect(store.connections).toHaveLength(0)
+  })
+})

frontend/src/stores/cloudConnections.js

@@ -0,0 +1,39 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import * as api from '../api/client.js'
+
+export const useCloudConnectionsStore = defineStore('cloudConnections', () => {
+  const connections = ref([])
+  const loading = ref(false)
+  const error = ref(null)
+
+  async function fetchConnections() {
+    loading.value = true
+    error.value = null
+    try {
+      const data = await api.listCloudConnections()
+      connections.value = data.items ?? []
+    } catch (e) {
+      error.value = e.message || 'Failed to load cloud connections'
+    } finally {
+      loading.value = false
+    }
+  }
+
+  async function disconnect(id) {
+    try {
+      await api.disconnectCloud(id)
+      connections.value = connections.value.filter(c => c.id !== id)
+    } catch (e) {
+      throw e
+    }
+  }
+
+  async function disconnectAll() {
+    const ids = connections.value.map(c => c.id)
+    for (const id of ids) await disconnect(id)
+    connections.value = []
+  }
+
+  return { connections, loading, error, fetchConnections, disconnect, disconnectAll }
+})