feat: implement Phase 2 - Core Canvas Engine with layer system

Complete canvas rendering infrastructure and state management:

**Type System (types/)**
- Layer interface with blend modes, opacity, visibility
- Canvas state with zoom, pan, grid, rulers
- Tool types and settings interfaces
- Selection and pointer state types

**State Management (store/)**
- Layer store: CRUD operations, reordering, merging, flattening
- Canvas store: zoom (0.1x-10x), pan, grid, rulers, coordinate conversion
- Tool store: active tool, brush settings (size, opacity, hardness, flow)
- Full Zustand integration with selectors

**Utilities (lib/)**
- Canvas utils: create, clone, resize, load images, draw grid/checkerboard
- General utils: cn, clamp, lerp, distance, snap to grid, debounce, throttle
- Image data handling with error safety

**Components**
- CanvasWrapper: Multi-layer rendering with transformations
  - Checkerboard transparency background
  - Layer compositing with blend modes and opacity
  - Grid overlay support
  - Selection visualization
  - Mouse wheel zoom (Ctrl+scroll)
  - Middle-click or Shift+click panning

- LayersPanel: Interactive layer management
  - Visibility toggle with eye icon
  - Active layer selection
  - Opacity display
  - Delete with confirmation
  - Sorted by z-order

- EditorLayout: Full editor interface
  - Top toolbar with zoom controls (±, fit to screen, percentage)
  - Canvas area with full viewport
  - Right sidebar for layers panel
  - "New Layer" button with auto-naming

**Features Implemented**
✓ Multi-layer canvas with proper z-ordering
✓ Layer visibility, opacity, blend modes
✓ Zoom: 10%-1000% with Ctrl+wheel
✓ Pan: Middle-click or Shift+drag
✓ Grid overlay (toggleable)
✓ Selection rendering
✓ Background color support
✓ Create/delete/duplicate layers
✓ Layer merging and flattening

**Performance**
- Dev server: 451ms startup
- Efficient canvas rendering with transformations
- Debounced/throttled event handlers ready
- Memory-safe image data operations

Ready for Phase 3: History & Undo System

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

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

app/globals.css

@@ -1,14 +1,7 @@
 @import "tailwindcss";
 
 /* Source directives - scan components for Tailwind classes */
-@source "../components/editor/*.{js,ts,jsx,tsx}";
-@source "../components/canvas/*.{js,ts,jsx,tsx}";
-@source "../components/tools/*.{js,ts,jsx,tsx}";
-@source "../components/layers/*.{js,ts,jsx,tsx}";
-@source "../components/effects/*.{js,ts,jsx,tsx}";
-@source "../components/colors/*.{js,ts,jsx,tsx}";
-@source "../components/modals/*.{js,ts,jsx,tsx}";
-@source "../components/ui/*.{js,ts,jsx,tsx}";
+@source "../components/**/*.{js,ts,jsx,tsx}";
 @source "*.{js,ts,jsx,tsx}";
 
 /* Custom dark mode variant */