fix(unique-fields): remove @CloseDBIfOpened to restore atomicity with contentlet save (#35567)

## Problem

Closes #35566

`DBUniqueFieldValidationStrategy.innerValidate()` was annotated with
both `@WrapInTransaction` **and** `@CloseDBIfOpened`. The combination
has a critical side-effect:

- `@CloseDBIfOpened` closes any existing JDBC connection and opens a
**fresh one**, isolated from the caller's transaction.
- `@WrapInTransaction` then starts and **commits** a new transaction on
that fresh connection.

This means the `INSERT INTO unique_fields` commits **independently** of
the outer contentlet save transaction. If the outer transaction is later
rolled back (e.g., a failure mid-save, or a startup migration task that
rolls back), the `unique_fields` row persists as a permanent **orphan**
— a hash pointing to a contentlet that no longer exists.

```
Outer transaction (contentlet save):
  ├── INSERT contentlet          → connection A (outer tx)
  ├── innerValidate()
  │   ├── @CloseDBIfOpened opens connection B
  │   ├── INSERT unique_fields   → connection B ← COMMITS HERE ✗
  │   └── closes connection B
  └── ROLLBACK outer tx
       ├── contentlet rolled back ✓
       └── unique_fields row stays ✗  (already committed on B)
```

On the next contentlet save or migration run, `findVariable()` returns
empty (no contentlet exists), but `publish()` / `save()` hits a
duplicate-key violation on `unique_fields_pkey`, incorrectly blocking a
valid operation.

## Fix

Remove `@CloseDBIfOpened` from `innerValidate()` and
`innerValidateInPreview()`.

With only `@WrapInTransaction`, the interceptor **joins the caller's
existing transaction** if one is active. The `unique_fields` INSERT and
the contentlet save are now **atomic** — a rollback of the outer
transaction rolls back both.

When no outer transaction is present, `@WrapInTransaction` starts its
own, preserving the existing behavior.

```
Outer transaction (contentlet save):
  ├── INSERT contentlet          → connection A (outer tx)
  ├── innerValidate() (@WrapInTransaction joins outer tx)
  │   └── INSERT unique_fields   → connection A (same tx) ✓
  └── COMMIT/ROLLBACK outer tx
       ├── contentlet committed/rolled back ✓
       └── unique_fields committed/rolled back ✓  (atomic)
```

## Impact

- Prevents new orphaned `unique_fields` rows from being created on any
contentlet save rollback.
- Existing orphans in the database are not cleaned up by this PR (a
separate cleanup utility or migration would be needed for that).
- The companion PR #35565 addresses the cascade blast radius caused by
existing orphans in the language variable migration.

## Files changed

-
`dotCMS/src/main/java/com/dotcms/contenttype/business/uniquefields/extratable/DBUniqueFieldValidationStrategy.java`
- Removed `@CloseDBIfOpened` from `innerValidate()` and
`innerValidateInPreview()`
  - Removed unused `import com.dotcms.business.CloseDBIfOpened`

## Test plan
- [ ] Save a contentlet with a unique field — verify `unique_fields` row
is inserted
- [ ] Roll back the save (e.g., via an outer transaction) — verify the
`unique_fields` row is also absent after rollback
- [ ] Run existing `DBUniqueFieldValidationStrategy` integration tests —
no regressions
- [ ] Verify that duplicate-key enforcement still works correctly after
the change

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: fabrizzio-dotCMS

dotCMS/src/main/java/com/dotcms/contenttype/business/uniquefields/extratable/DBUniqueFieldValidationStrategy.java

@@ -7,7 +7,6 @@
 import static com.dotmarketing.util.Constants.DONT_RESPECT_FRONT_END_ROLES;
 import static com.liferay.util.StringPool.BLANK;
 
-import com.dotcms.business.CloseDBIfOpened;
 import com.dotcms.business.WrapInTransaction;
 import com.dotcms.contenttype.business.UniqueFieldValueDuplicatedException;
 import com.dotcms.contenttype.business.uniquefields.UniqueFieldValidationStrategy;
@@ -63,7 +62,6 @@ public DBUniqueFieldValidationStrategy(final  UniqueFieldDataBaseUtil uniqueFiel
 
     @Override
     @WrapInTransaction
-    @CloseDBIfOpened
     public void innerValidate(final Contentlet contentlet, final Field field, final Object fieldValue,
                        final ContentType contentType) throws UniqueFieldValueDuplicatedException, DotDataException, DotSecurityException {
 
@@ -77,7 +75,6 @@ public void innerValidate(final Contentlet contentlet, final Field field, final
 
     @Override
     @WrapInTransaction
-    @CloseDBIfOpened
     public void innerValidateInPreview(final Contentlet contentlet, final Field field, final Object fieldValue,
                                         final ContentType contentType)
             throws UniqueFieldValueDuplicatedException, DotDataException, DotSecurityException {