feat: platform admin frontend — pages, composables, navigation, impersonation

Build the frontend for platform admin in apps/app/:
- TypeScript types (admin.ts) and API composable (useAdmin.ts) with
  TanStack Query for all admin endpoints
- ImpersonationStore (Pinia) + ImpersonationBanner component integrated
  in the main layout, with token-based session management
- Platform navigation section (conditionally shown for super_admin users)
- Route guard blocking /platform/* for non-super_admin users
- 6 pages: dashboard with stats cards, organisations list/detail,
  users list/detail with impersonation, activity log with expandable rows
- All pages implement loading/error/empty states per conventions
- Vite build passes cleanly

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/app/src/composables/api/useAdmin.ts

@@ -0,0 +1,198 @@
+import { useMutation, useQuery, useQueryClient } from '@tanstack/vue-query'
+import type { Ref } from 'vue'
+import { apiClient } from '@/lib/axios'
+import type {
+  ActivityLogEntry,
+  AdminOrganisation,
+  AdminUser,
+  ImpersonationResponse,
+  PlatformStats,
+  UpdateAdminOrganisationPayload,
+  UpdateAdminUserPayload,
+} from '@/types/admin'
+
+interface ApiResponse<T> {
+  success: boolean
+  data: T
+  message?: string
+}
+
+interface PaginatedResponse<T> {
+  data: T[]
+  links: Record<string, string | null>
+  meta: {
+    current_page: number
+    per_page: number
+    total: number
+    last_page: number
+  }
+}
+
+// ─── Organisations ──────────────────────────────────────────
+
+export function useAdminOrganisations(params: Ref<Record<string, string | number | undefined>>) {
+  return useQuery({
+    queryKey: ['admin', 'organisations', params],
+    queryFn: async () => {
+      const { data } = await apiClient.get<PaginatedResponse<AdminOrganisation>>(
+        '/admin/organisations',
+        { params: params.value },
+      )
+      return data
+    },
+  })
+}
+
+export function useAdminOrganisation(id: Ref<string>) {
+  return useQuery({
+    queryKey: ['admin', 'organisations', id],
+    queryFn: async () => {
+      const { data } = await apiClient.get<ApiResponse<AdminOrganisation>>(
+        `/admin/organisations/${id.value}`,
+      )
+      return data.data
+    },
+    enabled: () => !!id.value,
+  })
+}
+
+export function useUpdateAdminOrganisation() {
+  const queryClient = useQueryClient()
+
+  return useMutation({
+    mutationFn: async ({ id, payload }: { id: string; payload: UpdateAdminOrganisationPayload }) => {
+      const { data } = await apiClient.put<ApiResponse<AdminOrganisation>>(
+        `/admin/organisations/${id}`,
+        payload,
+      )
+      return data.data
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin', 'organisations'] })
+    },
+  })
+}
+
+export function useDeleteAdminOrganisation() {
+  const queryClient = useQueryClient()
+
+  return useMutation({
+    mutationFn: async (id: string) => {
+      await apiClient.delete(`/admin/organisations/${id}`)
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin', 'organisations'] })
+    },
+  })
+}
+
+// ─── Users ──────────────────────────────────────────────────
+
+export function useAdminUsers(params: Ref<Record<string, string | number | undefined>>) {
+  return useQuery({
+    queryKey: ['admin', 'users', params],
+    queryFn: async () => {
+      const { data } = await apiClient.get<PaginatedResponse<AdminUser>>(
+        '/admin/users',
+        { params: params.value },
+      )
+      return data
+    },
+  })
+}
+
+export function useAdminUser(id: Ref<string>) {
+  return useQuery({
+    queryKey: ['admin', 'users', id],
+    queryFn: async () => {
+      const { data } = await apiClient.get<ApiResponse<AdminUser>>(
+        `/admin/users/${id.value}`,
+      )
+      return data.data
+    },
+    enabled: () => !!id.value,
+  })
+}
+
+export function useUpdateAdminUser() {
+  const queryClient = useQueryClient()
+
+  return useMutation({
+    mutationFn: async ({ id, payload }: { id: string; payload: UpdateAdminUserPayload }) => {
+      const { data } = await apiClient.put<ApiResponse<AdminUser>>(
+        `/admin/users/${id}`,
+        payload,
+      )
+      return data.data
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin', 'users'] })
+    },
+  })
+}
+
+export function useDeleteAdminUser() {
+  const queryClient = useQueryClient()
+
+  return useMutation({
+    mutationFn: async (id: string) => {
+      await apiClient.delete(`/admin/users/${id}`)
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin', 'users'] })
+    },
+  })
+}
+
+// ─── Stats ──────────────────────────────────────────────────
+
+export function usePlatformStats() {
+  return useQuery({
+    queryKey: ['admin', 'stats'],
+    queryFn: async () => {
+      const { data } = await apiClient.get<{ data: PlatformStats }>(
+        '/admin/stats',
+      )
+      return data.data
+    },
+  })
+}
+
+// ─── Activity Log ───────────────────────────────────────────
+
+export function useAdminActivityLog(params: Ref<Record<string, string | number | undefined>>) {
+  return useQuery({
+    queryKey: ['admin', 'activity-log', params],
+    queryFn: async () => {
+      const { data } = await apiClient.get<PaginatedResponse<ActivityLogEntry>>(
+        '/admin/activity-log',
+        { params: params.value },
+      )
+      return data
+    },
+  })
+}
+
+// ─── Impersonation ──────────────────────────────────────────
+
+export function useStartImpersonation() {
+  return useMutation({
+    mutationFn: async (userId: string) => {
+      const { data } = await apiClient.post<ApiResponse<ImpersonationResponse>>(
+        `/admin/impersonate/${userId}`,
+      )
+      return data.data
+    },
+  })
+}
+
+export function useStopImpersonation() {
+  return useMutation({
+    mutationFn: async () => {
+      const { data } = await apiClient.post<ApiResponse<{ user: AdminUser }>>(
+        '/admin/stop-impersonation',
+      )
+      return data.data
+    },
+  })
+}