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/types/account.ts

@@ -0,0 +1,62 @@
+export interface Account {
+  id: string
+  name: string
+  display_code: string
+  owner_id: string
+  created_at: string
+  updated_at: string
+}
+
+export interface Subscription {
+  id: string
+  account_id: string
+  plan: 'free' | 'pro' | 'team'
+  status: 'active' | 'past_due' | 'canceled' | 'trialing' | 'orphaned'
+  current_period_start: string | null
+  current_period_end: string | null
+  created_at: string
+  updated_at: string
+}
+
+export interface PlanLimits {
+  plan: string
+  max_trees: number | null
+  max_sessions_per_month: number | null
+  max_users: number | null
+  custom_branding: boolean
+  priority_support: boolean
+  export_formats: string[]
+}
+
+export interface SubscriptionDetails {
+  subscription: Subscription
+  limits: PlanLimits
+  usage: {
+    tree_count: number
+    session_count_this_month: number
+    user_count: number
+  }
+}
+
+export interface AccountInvite {
+  id: string
+  account_id: string
+  email: string
+  role: 'engineer' | 'viewer'
+  code: string
+  invited_by_id: string
+  accepted_by_id: string | null
+  expires_at: string
+  used_at: string | null
+  created_at: string
+}
+
+export interface AccountMember {
+  id: string
+  email: string
+  name: string
+  account_role: string
+  is_active: boolean
+  created_at: string
+  last_login: string | null
+}

frontend/src/types/category.ts

@@ -5,7 +5,7 @@ export interface Category {
   name: string
   slug: string
   description: string | null
-  team_id: string | null
+  account_id: string | null
   display_order: number
   is_active: boolean
   created_at: string
@@ -18,7 +18,7 @@ export interface CategoryListItem {
   name: string
   slug: string
   description: string | null
-  team_id: string | null
+  account_id: string | null
   display_order: number
   is_active: boolean
   tree_count: number
@@ -27,7 +27,7 @@ export interface CategoryListItem {
 export interface CategoryCreate {
   name: string
   description?: string | null
-  team_id?: string | null
+  account_id?: string | null
 }
 
 export interface CategoryUpdate {

frontend/src/types/index.ts

@@ -7,6 +7,7 @@ export * from './tag'
 export * from './category'
 export * from './folder'
 export * from './step'
+export type { Account, Subscription, PlanLimits, SubscriptionDetails, AccountInvite, AccountMember } from './account'
 
 // API response wrapper types
 export interface PaginatedResponse<T> {

frontend/src/types/step.ts

@@ -56,7 +56,7 @@ export interface StepCategory {
   name: string
   description?: string
   display_order: number
-  team_id?: string
+  account_id?: string
   is_active: boolean
 }
 

frontend/src/types/tag.ts

@@ -4,7 +4,7 @@ export interface Tag {
   id: string
   name: string
   slug: string
-  team_id: string | null
+  account_id: string | null
   usage_count: number
   created_at: string
 }
@@ -13,13 +13,13 @@ export interface TagListItem {
   id: string
   name: string
   slug: string
-  team_id: string | null
+  account_id: string | null
   usage_count: number
 }
 
 export interface TagCreate {
   name: string
-  team_id?: string | null
+  account_id?: string | null
 }
 
 export interface TagAssignment {

frontend/src/types/tree.ts

@@ -67,7 +67,7 @@ export interface Tree {
   tags: string[]
   tree_structure: TreeStructure
   author_id: string | null
-  team_id: string | null
+  account_id: string | null
   is_active: boolean
   is_public: boolean
   is_default: boolean
@@ -86,7 +86,7 @@ export interface TreeListItem {
   category_info: CategoryInfo | null
   tags: string[]
   author_id: string | null
-  team_id: string | null
+  account_id: string | null
   is_active: boolean
   is_public: boolean
   is_default: boolean

frontend/src/types/user.ts

@@ -6,8 +6,8 @@ export interface User {
   name: string
   role: UserRole
   is_super_admin: boolean
-  is_team_admin: boolean
-  team_id: string | null
+  account_id: string
+  account_role: 'owner' | 'engineer' | 'viewer'
   created_at: string
   last_login: string | null
 }