Implement deep query planner/executor for nested where conditions

[konard]

Summary

• Implements comprehensive deep query processing for nested where conditions as requested in issue Deep query planner/executor #7
• Adds support for all logical operators: _and, _or, _not
• Enables nested relationship filtering: from, to, type, in, out
• Supports all comparison operators: _eq, _neq, _gt, _gte, _lt, _lte, _in, _nin, _is_null
• Fixes type inconsistency in LinksBooleanExpression.type_id field
• Maintains full backward compatibility with existing queries

Implementation Details

• Deep Query Processing: Completely rewrote LinksQuery.GetLinks() to handle complex nested where clauses
• Recursive Evaluation: Added EvaluateWhereClause() method that recursively processes nested conditions
• Relationship Navigation: Implemented support for filtering by properties of linked objects (from.id, to.id, etc.)
• Performance Optimization: Uses basic query optimization to reduce candidate set before applying complex filters

Examples of Supported Queries

Logical Operators

{
  links(where: {
    _and: [
      { id: { _gt: 0 } }
      { from_id: { _eq: 1 } }
    ]
  }) { id from_id to_id }
}

Nested Relationships

{
  links(where: {
    from: { id: { _gt: 0 } }
    to: { id: { _lt: 100 } }
  }) { 
    id from_id to_id 
    from { id }
    to { id }
  }
}

Outgoing/Incoming Links

{
  links(where: {
    out: { to_id: { _gt: 0 } }
    in: { from_id: { _gt: 0 } }
  }) {
    id from_id to_id
    out { id to_id }
    in { id from_id }
  }
}

Test Coverage

• Added 8 comprehensive test cases covering deep query functionality
• All existing tests continue to pass (maintains backward compatibility)
• Total test results: 11/11 query tests pass, 5/5 mutation tests pass

Bug Fixes

• Fixed type mismatch: LinksBooleanExpression.type_id now correctly uses LongComparisonExpression instead of LinksBooleanExpression

🤖 Generated with Claude Code

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Resolves #7