feat(tools): implement advanced brush tools - Clone Stamp, Smudge, and Dodge/Burn

Added three professional-grade image manipulation tools to complete Feature 4:

Clone Stamp Tool (Shortcut: 8)
- Sample from source location with Alt+Click
- Paint sampled content to destination
- Maintains relative offset for natural cloning
- Supports soft/hard brush with hardness setting

Smudge Tool (Shortcut: 9)
- Creates realistic paint-smearing effects
- Progressively blends colors for natural smudging
- Uses flow setting to control smudge strength
- Soft brush falloff for smooth blending

Dodge/Burn Tool (Shortcut: 0)
- Dodge mode: Lightens image areas (default)
- Burn mode: Darkens image areas (Alt key)
- Professional photography exposure adjustment
- Respects hardness setting for precise control

All tools:
- Fully integrated with tool palette and keyboard shortcuts
- Support smooth interpolation for fluid strokes
- Use existing tool settings (size, opacity, hardness, flow, spacing)
- Lazy-loaded via code splitting system
- Icons from Lucide React (Stamp, Droplet, Sun)

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

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

components/tools/tool-palette.tsx

@@ -10,6 +10,9 @@ import {
   MousePointer,
   Pipette,
   Type,
+  Stamp,
+  Droplet,
+  Sun,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
 
@@ -21,6 +24,9 @@ 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: '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' },
 ];
 
 export function ToolPalette() {