Simplify Validator interface with centralized field handling

[sivchari]

Description

Refactor the Validator interface to eliminate redundancy and centralize field information handling.

Implementation Details

New interface design:

type Validator interface {
    Validate(field *FieldInfo) ValidationCheck
}

type FieldInfo struct {
    Name       string
    Type       types.Type
    StructName string
    Path       string
}

type ValidationCheck struct {
    Condition string   // "len(t.Name) == 0"
    ErrorType string   // "required"
    Reason    string   // "field is required"
    Imports   []string // ["unicode/utf8"]
}

Benefits:

• Validators no longer duplicate field information
• Error generation logic is centralized
• Easier to implement new validators

Success Criteria

• All existing validators migrated to new interface
• Reduced code duplication
• Simplified validator implementations