feat(web): add workspace management UI (M2 #12)

- Create workspace listing page at /settings/workspaces
  - List all user workspaces with role badges
  - Create new workspace functionality
  - Display member count per workspace

- Create workspace detail page at /settings/workspaces/[id]
  - Workspace settings (name, ID, created date)
  - Member management with role editing
  - Invite member functionality
  - Delete workspace (owner only)

- Add workspace components:
  - WorkspaceCard: Display workspace info with role badge
  - WorkspaceSettings: Edit workspace settings and delete
  - MemberList: Display and manage workspace members
  - InviteMember: Send invitations with role selection

- Add WorkspaceMemberWithUser type to shared package
- Follow existing app patterns for styling and structure
- Use mock data (ready for API integration)

apps/api/src/app.module.ts

@@ -13,6 +13,7 @@ import { IdeasModule } from "./ideas/ideas.module";
 import { WidgetsModule } from "./widgets/widgets.module";
 import { LayoutsModule } from "./layouts/layouts.module";
 import { KnowledgeModule } from "./knowledge/knowledge.module";
+import { UsersModule } from "./users/users.module";
 
 @Module({
   imports: [
@@ -28,6 +29,7 @@ import { KnowledgeModule } from "./knowledge/knowledge.module";
     WidgetsModule,
     LayoutsModule,
     KnowledgeModule,
+    UsersModule,
   ],
   controllers: [AppController],
   providers: [AppService],