feat: migrate ConnectedAccount infrastructure entities to metadata schema (#18784)

## Summary

- Migrates 4 entities (`connectedAccount`, `messageChannel`,
`calendarChannel`, `messageFolder`) from per-workspace schemas to the
shared `core` metadata schema
- Introduces a `IS_CONNECTED_ACCOUNT_MIGRATED` feature flag to control
the migration: when enabled, reads come from core metadata and all
writes are dual-written to both workspace and core
- Extracts 12 enums from workspace entity files to `twenty-shared` for
reuse across frontend and backend
- Creates new TypeORM entities, metadata services, GraphQL
resolvers/DTOs, and exception interceptors per entity
- Each entity owns its own data access module
(`ConnectedAccountDataAccessModule`, `MessageChannelDataAccessModule`,
`CalendarChannelDataAccessModule`, `MessageFolderDataAccessModule`) — no
umbrella infrastructure module
- Adds a 1.20 upgrade command that backfills data from workspace schemas
to core (preserving UUIDs) and enables the feature flag
- Replaces direct repository access with data access service calls
across ~50 files in messaging, calendar, and connected-account modules
- Adds `lastSignedInAt` and `oidcTokenClaims` fields to the new
`ConnectedAccountEntity`
- Drops unused `lastSyncHistoryId` field from the migrated connected
account entity

## Test plan

- [x] Lint passes (`npx nx lint:diff-with-main twenty-server`)
- [x] Typecheck passes (`npx nx typecheck twenty-server`)
- [x] All unit tests pass (477 suites, 4267 tests, 0 failures)
- [ ] Manual test: verify messaging sync works with feature flag
disabled (existing behavior)
- [ ] Manual test: run upgrade command on a workspace, verify data
backfilled to core tables
- [ ] Manual test: verify messaging/calendar sync works with feature
flag enabled (dual-write path)
- [ ] Manual test: verify GraphQL metadata resolvers return correct data
when flag enabled

packages/twenty-server/src/engine/twenty-orm/entity-manager/workspace-entity-manager.spec.ts

@@ -250,6 +250,7 @@ describe('WorkspaceEntityManager', () => {
         IS_DATE_TIME_WHOLE_DAY_FILTER_ENABLED: false,
         IS_DRAFT_EMAIL_ENABLED: false,
         IS_RICH_TEXT_V1_MIGRATED: false,
+        IS_CONNECTED_ACCOUNT_MIGRATED: false,
       },
       userWorkspaceRoleMap: {},
       eventEmitterService: {