fix(i18n): restore validation messages masked by duplicate top-level lang key [3.x]

[ManukMinasyan]

Summary

resources/lang/en/custom-fields.php had two top-level 'validation' => [...] blocks at lines 131 and 544. PHP silently keeps only the last occurrence of duplicate array keys, so the 11-key block at the bottom wiped out the 200+ key block above it — including 'unique_value' (line 355).

User-visible symptom on Edit Order (and any model using unique custom-field validation):

custom-fields::custom-fields.validation.unique_value

…was rendered verbatim instead of the translated message, because __() couldn't resolve the key.

Changes

• resources/lang/en/custom-fields.php — merged the 11 capability labels (min_length, max_length, min_value, max_value, min_selections, max_selections, max_file_size_kb, accepted_file_types, accepted_file_types_placeholder, decimal_places, decimal_places_placeholder) into the canonical validation block at line 131, then removed the duplicate block. No keys lost.
• tests/Feature/Translations/LanguageKeysTest.php — added a structural test that scans every resources/lang/<locale>/*.php for duplicate top-level keys and asserts none exist. Existing key-existence tests didn't catch this because none of the listed keys happened to live in the masked block.

Test plan

• vendor/bin/pest tests/Feature/Translations/ — 131 passed
• Manually injected a single-quoted duplicate 'validation' block; new test fails with: Duplicate top-level key(s) in en/custom-fields.php: validation. PHP keeps only the last definition, masking earlier values.
• Removed the injection; test passes.
• In-browser verification at /shop/orders/3/edit (filament-demo): entering a duplicate email in an Email Unique custom field now displays The value "armen@gmail.com" is already assigned to another record. instead of the raw key.
• vendor/bin/pint --dirty — pass

[Copilot]

Pull request overview

This PR fixes a Laravel translation regression caused by a duplicate top-level array key in resources/lang/en/custom-fields.php, where PHP silently kept only the last 'validation' block and masked the earlier (canonical) one—resulting in raw translation keys being shown to users.

Changes:

• Merged the small duplicate 'validation' block into the canonical 'validation' section and removed the duplicate definition.
• Added a Pest test to detect duplicate top-level keys across all resources/lang/<locale>/*.php files to prevent similar masking issues.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
resources/lang/en/custom-fields.php	Removes the duplicate top-level validation key by merging entries into the canonical block, restoring masked translations like unique_value.
tests/Feature/Translations/LanguageKeysTest.php	Adds a structural safeguard test that scans language files for duplicate top-level keys that PHP would otherwise silently overwrite.