Deprecate asExpression from field metadata search_vector (#22287)

## Summary

Fully deprecates the cached `asExpression` / `generatedType` settings on
`TS_VECTOR` (searchVector) fields. Previously the generated-column
expression was stored in `FieldMetadataSettings` and kept in sync via
imperative recompute side-effects. It is now **derived at DDL time**
from the `searchFieldMetadata` rows that describe which fields feed the
search vector, making `searchFieldMetadata` the single source of truth
and removing a whole class of cache-drift bugs.

This is delivered across the milestones tracked in #2587 and coordinates
with the frontend migration (#1428).

## Why

- The searchVector expression lived in two places (stored
`settings.asExpression` + the actual generated column), kept consistent
by bespoke side-effects (`recompute-search-vector-on-field-rename`,
label-identifier recompute, etc.).
- The frontend reconstructed the searchable-fields list by
**regex-parsing** the stored `asExpression`.
- Both are brittle. Deriving the expression from `searchFieldMetadata`
rows at build/run time removes the cache and the parsing.

## What changed

### Server - data model & derivation
- Introduce the `tsVectorFieldMetadata` relation on
`searchFieldMetadata` (`tsVectorFieldMetadataId` / universal identifier)
linking each searchable-field row to its target `TS_VECTOR` field.
- New runtime derivation
`deriveSearchVectorAsExpressionForTsVectorField`
(`flat-search-field-metadata/utils/...`) used by the create-object and
update-field handlers to generate the column expression from
`searchFieldMetadata` rows.
- Remove `asExpression` / `generatedType` from stored settings:
`FieldMetadataSettings.TS_VECTOR` is now `null`; the column builder
(`generate-column-definitions.util.ts`) hardcodes `generatedType:
'STORED'` and requires the derived expression.
- Delete the imperative recompute side-effects and the
`compute-search-vector-universal-settings-from-object-manifest` path;
drop the `settings` block from all 28 standard
`compute-*-standard-flat-field-metadata` utils.

### Server - migration runner
- New `rebuildSearchVector` marker on `update-field` actions: the
orchestrator synthesizes targeted column rebuilds
(`compute-search-vector-rebuild-target-universal-identifiers.util.ts` +
the deprioritize aggregator) only when a searchFieldMetadata change or
indexed-field rename actually requires it - instead of rebuilding on
every settings touch.
- Deferrable FKs + in-flight ID resolution so a `searchFieldMetadata`
row and its `TS_VECTOR` field can be created in the same transaction
(deterministic UUIDs).

### Frontend (contract change, #1428)
- New `SearchFieldMetadataDTO` + dataloader exposing
`searchFieldMetadataList` on object metadata.
- `SettingsObjectSearchSection` now reads
`objectMetadataItem.searchFieldMetadatas` instead of parsing
`asExpression`; new `SearchFieldMetadataItem` type, fragment, and
mapping updates.

### Upgrade commands (2.18)
-
`2-18-instance-command-fast-...-add-ts-vector-field-metadata-id-to-search-field-metadata`
-
`2-18-instance-command-fast-...-make-search-field-metadata-fks-deferrable`
-
`2-18-instance-command-slow-...-backfill-ts-vector-field-metadata-id-on-search-field-metadata`

(These were relocated from 2.16 to 2.18 and re-timestamped into an
ordered block - add column -> make FK deferrable -> backfill data -
since 2.16/2.17 are released.)

### Tests
- Updated search-vector side-effect integration specs to assert behavior
(search works) rather than the now-removed `asExpression`; removed the
obsolete expression-validation specs; refreshed the application-sync
snapshot (`universalSettings: null`).

## Upgrade / compatibility notes
- Existing workspaces keep their stored `settings` until a later
cleanup; nothing reads it anymore. The new derivation drives all DDL
going forward.
- Schema changes are gated behind the 2.18 instance commands above.

## Known follow-up (separate PR)
https://github.com/twentyhq/core-team-issues/issues/2620
- The column rebuild (`DROP`/`ADD` of the `searchVector` STORED column)
cascade-drops its GIN index and does not recreate it - a pre-existing
regression on `main` inherited here. A follow-up PR will fix the rebuild
handler to recreate the GIN index and add a 2.18 workspace command to
recompute every search vector + strip the deprecated settings.
(Planned.)

## Test plan
- [ ] `npx nx typecheck twenty-server` / `twenty-front`
- [ ] `npx nx lint:diff-with-main twenty-server` / `twenty-front`
- [ ] Server integration: create/update/delete field, rename indexed
field, update object - search returns expected records
- [ ] Run the 2.18 instance commands on a seeded DB; verify
`tsVectorFieldMetadataId` backfilled and FKs deferrable
- [ ] Frontend: object Search settings tab lists the correct searchable
fields (no `asExpression` parsing)

close https://github.com/twentyhq/core-team-issues/issues/2587

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packages/twenty-server/src/database/commands/upgrade-version-command/instance-commands.constant.ts

@@ -34,6 +34,13 @@ import { AddIsSystemSideEffectFastInstanceCommand } from 'src/database/commands/
 import { BackfillConnectionSecuritySlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-15/2-15-instance-command-slow-1781461753981-backfill-connection-security';
 import { AddChannelWebhookSubscriptionFieldsFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782152096938-add-channel-webhook-subscription-fields';
 import { AddUniversalIdentifierAndApplicationIdToSearchFieldMetadataFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782200000000-add-universal-identifier-and-application-id-to-search-field-metadata';
+import { AddServerTriggerSettingsToLogicFunctionFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782211913427-add-server-trigger-settings-to-logic-function';
+import { AddPrimaryPublicDomainToApplicationFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782281874768-add-primary-public-domain-to-application';
+import { MakePublicDomainApplicationIdNotNullSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-slow-1782281874769-make-public-domain-application-id-not-null';
+import { CreateDpaAgreementCoreTableFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-17/2-17-instance-command-fast-1801000020000-create-dpa-agreement-core-table';
+import { CreateApplicationTranslationCoreTableFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-17/2-17-instance-command-fast-1801000100000-create-application-translation-core-table';
+import { AddTsVectorFieldMetadataIdToSearchFieldMetadataFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-18/2-18-instance-command-fast-1810000001000-add-ts-vector-field-metadata-id-to-search-field-metadata';
+import { BackfillTsVectorFieldMetadataIdOnSearchFieldMetadataSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-18/2-18-instance-command-slow-1810000003000-backfill-ts-vector-field-metadata-id-on-search-field-metadata';
 import { AddCacheTokensToAgentChatThreadFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-2/2-2-instance-command-fast-1777455269302-add-cache-tokens-to-agent-chat-thread';
 import { AddLogoToApplicationFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-2/2-2-instance-command-fast-1777539664664-add-logo-to-application';
 import { AddSubFieldNameToViewSortEarlyFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-3/2-3-instance-command-fast-1747234200000-add-sub-field-name-to-view-sort';
@@ -77,11 +84,6 @@ import { EncryptNonSecretApplicationVariableSlowInstanceCommand } from 'src/data
 import { MigrateAiModelPreferencesSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-9/2-9-instance-command-slow-1799000010000-migrate-ai-model-preferences';
 import { AddFolderImportToMessageFolderPendingSyncActionFastInstanceCommand } from './2-15/2-15-instance-command-fast-1781714499016-add-folder-import-to-message-folder-pending-sync-action';
 import { AddViewKanbanColumnWidthFastInstanceCommand } from './2-15/2-15-instance-command-fast-1781900000000-add-view-kanban-column-width';
-import { AddPrimaryPublicDomainToApplicationFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782281874768-add-primary-public-domain-to-application';
-import { MakePublicDomainApplicationIdNotNullSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-slow-1782281874769-make-public-domain-application-id-not-null';
-import { AddServerTriggerSettingsToLogicFunctionFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-16/2-16-instance-command-fast-1782211913427-add-server-trigger-settings-to-logic-function';
-import { CreateDpaAgreementCoreTableFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-17/2-17-instance-command-fast-1801000020000-create-dpa-agreement-core-table';
-import { CreateApplicationTranslationCoreTableFastInstanceCommand } from 'src/database/commands/upgrade-version-command/2-17/2-17-instance-command-fast-1801000100000-create-application-translation-core-table';
 
 export const INSTANCE_COMMANDS = [
   AddViewFieldGroupIdIndexOnViewFieldFastInstanceCommand,
@@ -166,4 +168,6 @@ export const INSTANCE_COMMANDS = [
   MakePublicDomainApplicationIdNotNullSlowInstanceCommand,
   CreateDpaAgreementCoreTableFastInstanceCommand,
   CreateApplicationTranslationCoreTableFastInstanceCommand,
+  AddTsVectorFieldMetadataIdToSearchFieldMetadataFastInstanceCommand,
+  BackfillTsVectorFieldMetadataIdOnSearchFieldMetadataSlowInstanceCommand,
 ];