feat(phase-13): implement crop tool with visual guides and handles

Add comprehensive crop tool with visual guides, resize handles, and Apply/Cancel UI.

Features:
- Interactive crop area selection with drag-to-create
- 8 resize handles (corners and edges) for precise cropping
- Visual overlay with dimmed areas outside crop region
- Rule of thirds grid overlay for composition guidance
- Drag crop area to reposition
- Apply/Cancel buttons in tool options
- White border and handles for clear visibility

Changes:
- Created tools/crop-tool.ts with CropTool class
- Added crop tool to lib/tool-loader.ts
- Added Crop icon and button to tool palette with 'C' shortcut
- Added crop tool options UI in components/editor/tool-options.tsx
- Exported CropTool from tools/index.ts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/tools/tool-palette.tsx

@@ -14,6 +14,7 @@ import {
   Stamp,
   Droplet,
   Sun,
+  Crop,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
 
@@ -26,6 +27,7 @@ const tools: { type: ToolType; icon: React.ReactNode; label: string; shortcut: s
   { type: 'eyedropper', icon: <Pipette className="h-5 w-5" />, label: 'Eyedropper', shortcut: '5' },
   { type: 'text', icon: <Type className="h-5 w-5" />, label: 'Text', shortcut: '6' },
   { type: 'select', icon: <MousePointer className="h-5 w-5" />, label: 'Select', shortcut: '7' },
+  { type: 'crop', icon: <Crop className="h-5 w-5" />, label: 'Crop', shortcut: 'C' },
   { type: 'clone', icon: <Stamp className="h-5 w-5" />, label: 'Clone Stamp (Alt+Click source)', shortcut: '8' },
   { type: 'smudge', icon: <Droplet className="h-5 w-5" />, label: 'Smudge', shortcut: '9' },
   { type: 'dodge', icon: <Sun className="h-5 w-5" />, label: 'Dodge/Burn (Alt for burn)', shortcut: '0' },