Fixed : Index audits, skip empty translation audits, and fix history preview - #508

Description

Creating an attribute returns a 504 on installs with a large audits table,
and viewing an attribute's History failed / showed noise.

Root cause

• AttributeTranslation and other translatable models use HistoryTrait, so
  creating one attribute writes one audit row per active locale. The
  audit_before_insert trigger runs two queries per insert filtering by
  (tags, history_id), which was never indexed — every insert is a full table
  scan, so creation times out as audits grows.
• Blank locales still produced empty audit rows (noise + trigger load).
• The History version preview crashed ("Array to string conversion") on a
  created version because the old value is an empty array, and it listed
  empty/default fields (validation, regex_pattern, ai_translate).

Changes

1. Add composite index on audits(tags, history_id) (prefix-aware, idempotent,
   MySQL + PostgreSQL). The trigger's two lookups become index lookups
   (EXPLAIN: type=ALL → type=ref, rows=1).
2. Override OwenIt's readyForAuditing() in HistoryTrait to skip auditing a
   translatable model when all of its historyTranslatableFields are empty.
   Non-translatable models (Attribute, Product, Category, …) are unaffected.
3. Guard AttributeHistoryPresenter::formatValue() against array (empty old)
   values so the created-version history no longer 500s.
4. Drop history rows that are empty on both sides so the preview shows only
   meaningful changes.
5. Add Pest tests: audits index/behaviour, the presenter, and the history
   preview across every attribute type.

Measured on ~2.1M audit rows: one attribute create dropped from ~138s to ~1.9s;
audit inserts per create dropped from 51 to 2.

How To Test This?

1. vendor/bin/pest packages/Webkul/Admin/tests/Feature/Catalog/AttributeAuditTest.php
2. vendor/bin/pest packages/Webkul/Admin/tests/Feature/Catalog/AttributeHistoryViewTest.php
3. Manually: Catalog → Attributes → Create Attribute → code + type + name → Save.
   Saves quickly even on a large audits table; open the History tab → view a
   version: it renders without error and omits empty fields.
4. SHOW INDEX FROM audits; shows audits_tags_history_id_index (tags, history_id).

Checklist

• vendor/bin/pest passes locally (new tests — 33 passed)

• vendor/bin/pint --test reports no style issues

• Target branch is master