PRE-3254: code quality fixing for level 6

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Description

Upgrade to PHP 8.4 syntax and fix CodeQuality
-> level 6 ✅ done
-> level 8 🎯 target

Motivation:
Related issue(s): Closes PRE-3254

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue) [ ]
• ✨ New feature (non-breaking change that adds functionality) [ ]
• 💥 Breaking change (fix or feature that causes existing functionality to change) [ ]
• 🔧 Refactor (no functional changes, code improvement only) [x]
• 📦 Dependency update [ ]
• 🔒 Security fix [ ]
• 📝 Documentation update [ ]

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Checklist

Code Quality

• Code is linted and formatted
• No unnecessary commented-out code or debug logs
• No hardcoded values (use env variables or config)

Testing

• Unit tests added / updated

Security & Ops

• No sensitive data or secrets introduced
• Logging and error handling are appropriate