feat: add encryptedKey column to Credential table for calendar integrations (#27154)

Adds encrypted credential storage using a new keyring system:
  - New `encryptedKey` column with AES-256-GCM encryption
  - Decryption in getCalendarsEvents with fallback to legacy `key`
  - buildCredentialCreateData service for credential creation
  - Phase 1: Google Calendar only, other integrations follow

apps/api/v2/src/ee/calendars/services/apple-calendar.service.ts

@@ -120,6 +120,7 @@ export class AppleCalendarService implements CredentialSyncCalendarApp {
         appId: APPLE_CALENDAR_ID,
         invalid: false,
         delegationCredentialId: null,
+        encryptedKey: null,
       };
 
       const dav = BuildCalendarService({

apps/api/v2/src/ee/calendars/services/ics-feed.service.ts

@@ -40,6 +40,7 @@ export class IcsFeedService implements ICSFeedCalendarApp {
       appId: ICS_CALENDAR,
       invalid: false,
       delegationCredentialId: null,
+      encryptedKey: null,
     };
 
     try {

apps/api/v2/src/modules/credentials/credentials.repository.ts

@@ -88,6 +88,7 @@ export class CredentialsRepository {
         id: true,
         type: true,
         key: true,
+        encryptedKey: true,
         userId: true,
         teamId: true,
         appId: true,