Add Kustomize-style patches support

[Copilot]

This PR implements Kustomize-style patches support for chartify, adding a unified patches field that can handle both Strategic Merge Patches and JSON Patches with automatic type detection.

Overview

The new Patches field in ChartifyOpts provides a modern, unified interface for applying patches that matches Kustomize's native patches functionality. This complements the existing JsonPatches and StrategicMergePatches fields while maintaining full backward compatibility.

Key Features

Auto-detection of Patch Types

Chartify automatically detects whether a patch is a Strategic Merge Patch or JSON Patch based on content structure:

• JSON Patches: Detected when content contains operations with op and path fields
• Strategic Merge Patches: Standard Kubernetes YAML resources

File-based and Inline Patches

// File-based patch
patches := []Patch{{Path: "./my-patch.yaml"}}

// Inline patch
patches := []Patch{{
    Patch: `apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 3`,
}}

Target Specification for JSON Patches

patches := []Patch{{
    Target: &PatchTarget{
        Kind: "Deployment", 
        Name: "myapp",
    },
    Patch: `- op: replace
  path: /spec/replicas
  value: 5`,
}}

CLI Integration

New --patch flag provides easy access to the patches functionality:

chartify myapp ./chart -o ./output --patch ./my-patch.yaml

Implementation Details

• New Types: Added Patch and PatchTarget structs to match Kustomize's patches field structure
• Auto-detection Logic: Implemented intelligent patch type detection in patch.go
• Kustomization Generation: Enhanced kustomization.yaml generation to handle the new unified patches format
• CLI Support: Extended the CLI with --patch flag for file-based patches

Testing

• Unit Tests: Comprehensive tests for patch struct validation and construction
• Integration Tests: End-to-end testing of strategic merge patches, inline patches, and JSON patches with targets
• CLI Testing: Manual verification of patch application and auto-detection
• Backward Compatibility: Verified existing --strategic-merge-patch and JsonPatches/StrategicMergePatches fields continue working

Backward Compatibility

This change is fully backward compatible:

• Existing JsonPatches and StrategicMergePatches fields continue to work unchanged
• Existing --strategic-merge-patch CLI flag continues to work unchanged
• All existing functionality preserved and tested

Fixes #94.

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