fix: upgrade calendar jest to v30 and add rate limiting to contacts/todo backends

- Calendar backend: upgrade jest 29→30 to fix broken pnpm symlink
  (jest 29 wasn't resolving in pnpm store, all 63 tests now pass)
- Contacts backend: add @nestjs/throttler (100 req/min)
- Todo backend: add @nestjs/throttler (100 req/min)
- Consistent rate limiting across all three backends (calendar already had it)

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

apps/contacts/apps/backend/package.json

@@ -30,6 +30,7 @@
 		"@nestjs/config": "^3.3.0",
 		"@nestjs/core": "^10.4.15",
 		"@nestjs/platform-express": "^10.4.15",
+		"@nestjs/throttler": "^6.2.1",
 		"class-transformer": "^0.5.1",
 		"class-validator": "^0.14.1",
 		"csv-parse": "^6.1.0",

apps/contacts/apps/backend/src/app.module.ts

@@ -1,5 +1,6 @@
 import { Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
+import { ThrottlerModule } from '@nestjs/throttler';
 import { MetricsModule } from '@manacore/shared-nestjs-metrics';
 import { DatabaseModule } from './db/database.module';
 import { ContactModule } from './contact/contact.module';
@@ -22,6 +23,12 @@ import { AdminModule } from './admin/admin.module';
 			isGlobal: true,
 			envFilePath: '.env',
 		}),
+		ThrottlerModule.forRoot([
+			{
+				ttl: 60000, // 60 seconds
+				limit: 100, // 100 requests per minute
+			},
+		]),
 		MetricsModule.register({
 			prefix: 'contacts_',
 			excludePaths: ['/health'],