Feat/operator strategies

[kettasoft]

Summary

Introduce a unified and extensible operator strategy pipeline for the Ruleset, Expression, and Tree engines.

Changes

• Add dedicated strategies for comparison, set, range, and null operators.
• Apply the same operator pipeline to direct and relational fields.
• Add support for not between.
• Accept both operator aliases and resolved SQL symbols in allowedOperators().
• Support custom operator strategies through Laravel's container.
• Improve Ruleset and Expression condition parsing.
• Preserve payload context when an operator value is invalid.
• Remove the unused legacy operator definition and mapper layers.
• Update configuration and documentation.