feat: update frontend for account-based subscriptions

Replace all team_id/team_admin references with account_id/owner across
types, store, hooks, API clients, components, and pages. Add new
AccountSettingsPage, UpgradePrompt, CheckoutButton, useSubscription
hook, and accounts API client. AuthStore now parallel-fetches account
and subscription data alongside user profile.

Also fix folder sidebar not refreshing after tree deletion by
dispatching the folder-changed event in handleDeleteTree.

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

frontend/src/api/accounts.ts

@@ -0,0 +1,48 @@
+import apiClient from './client'
+import type { Account, SubscriptionDetails, AccountMember, AccountInvite } from '@/types'
+
+export const accountsApi = {
+  async getMyAccount(): Promise<Account> {
+    const response = await apiClient.get<Account>('/accounts/me')
+    return response.data
+  },
+
+  async getMySubscription(): Promise<SubscriptionDetails> {
+    const response = await apiClient.get<SubscriptionDetails>('/accounts/me/subscription')
+    return response.data
+  },
+
+  async updateMyAccount(data: { name?: string }): Promise<Account> {
+    const response = await apiClient.patch<Account>('/accounts/me', data)
+    return response.data
+  },
+
+  async getMembers(): Promise<AccountMember[]> {
+    const response = await apiClient.get<AccountMember[]>('/accounts/me/members')
+    return response.data
+  },
+
+  async updateMemberRole(userId: string, role: string): Promise<AccountMember> {
+    const response = await apiClient.patch<AccountMember>(
+      `/accounts/me/members/${userId}/role`,
+      { role }
+    )
+    return response.data
+  },
+
+  async removeMember(userId: string): Promise<void> {
+    await apiClient.delete(`/accounts/me/members/${userId}`)
+  },
+
+  async createInvite(data: { email: string; role: string }): Promise<AccountInvite> {
+    const response = await apiClient.post<AccountInvite>('/accounts/me/invites', data)
+    return response.data
+  },
+
+  async getInvites(): Promise<AccountInvite[]> {
+    const response = await apiClient.get<AccountInvite[]>('/accounts/me/invites')
+    return response.data
+  },
+}
+
+export default accountsApi

frontend/src/api/categories.ts

@@ -2,9 +2,9 @@ import apiClient from './client'
 import type { Category, CategoryListItem, CategoryCreate, CategoryUpdate } from '@/types'
 
 export const categoriesApi = {
-  async list(includeInactive = false, teamOnly = false): Promise<CategoryListItem[]> {
+  async list(includeInactive = false, accountOnly = false): Promise<CategoryListItem[]> {
     const response = await apiClient.get<CategoryListItem[]>('/categories', {
-      params: { include_inactive: includeInactive, team_only: teamOnly },
+      params: { include_inactive: includeInactive, account_only: accountOnly },
     })
     return response.data
   },

frontend/src/api/index.ts

@@ -8,3 +8,4 @@ export { default as categoriesApi } from './categories'
 export { default as foldersApi } from './folders'
 export { default as stepsApi } from './steps'
 export { default as stepCategoriesApi } from './stepCategories'
+export { default as accountsApi } from './accounts'

frontend/src/api/tags.ts

@@ -2,16 +2,16 @@ import apiClient from './client'
 import type { Tag, TagListItem, TagCreate, TagAssignment } from '@/types'
 
 export const tagsApi = {
-  async list(includeTeam = true): Promise<TagListItem[]> {
+  async list(includeAccount = true): Promise<TagListItem[]> {
     const response = await apiClient.get<TagListItem[]>('/tags', {
-      params: { include_team: includeTeam },
+      params: { include_account: includeAccount },
     })
     return response.data
   },
 
-  async search(query: string, limit = 10, includeTeam = true): Promise<TagListItem[]> {
+  async search(query: string, limit = 10, includeAccount = true): Promise<TagListItem[]> {
     const response = await apiClient.get<TagListItem[]>('/tags/search', {
-      params: { q: query, limit, include_team: includeTeam },
+      params: { q: query, limit, include_account: includeAccount },
     })
     return response.data
   },