feat: implement comprehensive text tool (Phase 11)

Add complete text rendering system with the following features:

**Text Tool Core:**
- TextTool class with click-to-place text functionality
- Text cursor and pointer event handling
- Integration with DrawCommand for undo/redo support

**Text Rendering:**
- Multi-line text support with line height control
- Custom letter spacing
- Text alignment (left/center/right)
- Font families: 13 web-safe fonts + 14 popular Google Fonts
- Dynamic Google Font loading via Web Font Loader API
- Font styles (normal/italic) and weights (100-900)

**Text Dialog UI:**
- Full-featured text editor dialog
- Live preview of text with all formatting
- Font family selection (web-safe + Google Fonts)
- Font size (8-500px), style, and weight controls
- Color picker with hex input
- Text alignment options
- Line height slider (0.5-3x)
- Letter spacing slider (-10 to 50px)
- Multi-line text input with textarea

**State Management:**
- text-store with Zustand + persist middleware
- All text settings preserved across sessions
- Dialog state management (open/close)
- Click position tracking

**Integration:**
- Added text tool to tool palette with Type icon
- Registered TextTool in canvas tool system
- Added TextDialog to editor layout
- Full type safety with TypeScript interfaces

**Undoable:**
- Text rendering fully integrated with command pattern
- Each text insertion creates single undo point
- Proper before/after state capture

This completes Phase 11 of the implementation plan, marking
the transition from MVP to a fully-featured image editor.

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

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

components/tools/tool-palette.tsx

@@ -9,6 +9,7 @@ import {
   PaintBucket,
   MousePointer,
   Pipette,
+  Type,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
 
@@ -18,6 +19,7 @@ const tools: { type: ToolType; icon: React.ReactNode; label: string }[] = [
   { type: 'eraser', icon: <Eraser className="h-5 w-5" />, label: 'Eraser' },
   { type: 'fill', icon: <PaintBucket className="h-5 w-5" />, label: 'Fill' },
   { type: 'eyedropper', icon: <Pipette className="h-5 w-5" />, label: 'Eyedropper' },
+  { type: 'text', icon: <Type className="h-5 w-5" />, label: 'Text' },
   { type: 'select', icon: <MousePointer className="h-5 w-5" />, label: 'Select' },
 ];