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/users/users.module.ts

@@ -0,0 +1,16 @@
+import { Module } from "@nestjs/common";
+import { PreferencesController } from "./preferences.controller";
+import { PreferencesService } from "./preferences.service";
+import { PrismaModule } from "../prisma/prisma.module";
+import { AuthModule } from "../auth/auth.module";
+
+/**
+ * Module for user-related endpoints (preferences, etc.)
+ */
+@Module({
+  imports: [PrismaModule, AuthModule],
+  controllers: [PreferencesController],
+  providers: [PreferencesService],
+  exports: [PreferencesService],
+})
+export class UsersModule {}