feat: add BackedEnum support and housekeeping improvements

[enricodelazzari]

Summary

BackedEnum support

• Introduce MarkValue class with resolve() to normalize BackedEnum|string|null to ?string
• Add MarkValue::resolveAll() to normalize arrays, eliminating duplicated inline logic in hasAllowedValues()
• Update all Mark public methods (add, remove, count, has, toggle, hasAllowedValues) and Markable::scopeWhereHasMark() to accept null|string|\BackedEnum instead of ?string
• Support enum class strings as allowed_values config (resolves all cases automatically)
• Add tests/Enums/ReactionType.php and corresponding test coverage for all enum-based flows

Centralize config access via Support\Config

• Add src/Support/Config.php with typed static methods (getUserModel, getTablePrefix, getAllowedValues)
• Replace all scattered config('markable.*') calls in Mark.php and Markable.php

Housekeeping

• Migrate test suite from PHPUnit to Pest (tests/Pest.php, pestphp/pest)
• Replace Psalm with PHPStan (phpstan.neon.dist, analyse.yml workflow)
• Remove spatie/laravel-ray from dev dependencies
• Drop support for PHP < 8.3 and Laravel < 11
• Add .claude/ to .gitignore

Test plan

• composer test — all 36 tests pass
• can_add_a_reaction_with_backed_enum
• can_has_a_reaction_with_backed_enum
• can_remove_a_reaction_with_backed_enum
• can_toggle_a_reaction_with_backed_enum
• can_count_reactions_with_backed_enum
• can_use_enum_class_as_allowed_values
• cannot_add_invalid_value_when_allowed_values_is_enum_class

🤖 Generated with Claude Code