Fix: allow enum filters on relation queries

[RobertoNegro]

Problem

Applying EnumFilter or EnumBooleanFilter to a resource index rendered through a relation (e.g. a HasMany field on a detail page) throws:

TypeError: Datomatic\Nova\Fields\Enum\EnumBooleanFilter::apply(): Return value must be of type Illuminate\Database\Eloquent\Builder, Illuminate\Database\Eloquent\Relations\HasMany returned

Root cause

Nova may hand the filter an Illuminate\Database\Eloquent\Relations\Relation instead of a plain Builder. Relation::__call() forwards where() / whereIn() to the inner builder via forwardDecoratedCallTo(), which returns the relation itself, so the filter returns a HasMany, violating the : Builder return type.

Both classes implement Illuminate\Contracts\Database\Eloquent\Builder, the same type Nova's own Filter::apply() documents.

Fix

Return type widened from the concrete Eloquent builder to the contract it shares with relations. Two-line diff, behavior unchanged:

-use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Contracts\Database\Eloquent\Builder;

applied to src/EnumFilter.php and src/EnumBooleanFilter.php.

Verification

• Reproduced the TypeError on a HasMany relation before the fix; after the fix both filters apply cleanly on Builder and HasMany, an empty boolean selection stays a no-op, and the generated SQL is unchanged.
• php-cs-fixer --dry-run with the repo config: clean.
• PHPStan level max: no new issues (3 pre-existing notices gone).