fix: correct API integration and complete missing features

Fix API response format mismatches and implement all remaining features:

**API Integration Fixes:**
- Fix ManipulationPanel to use `colors` instead of `results` from API responses
- Fix gradient endpoint to use `gradient` array from API response
- Fix color blindness simulator to use correct field names (`input`/`output` vs `original`/`simulated`)
- Fix text color optimizer request field (`backgrounds` vs `background_colors`)
- Fix method name casing: `simulateColorBlindness` (capital B)
- Add palette generation endpoint integration

**Type Definition Updates:**
- Update GradientData to match API structure with `gradient` array
- Update ColorBlindnessData to use `colors` with `input`/`output`/`difference_percentage`
- Update TextColorData to use `colors` with `textcolor`/`wcag_aa`/`wcag_aaa` fields
- Add PaletteGenerateRequest and PaletteGenerateData types

**Completed Features:**
- Harmony Palettes: Now uses dedicated `/palettes/generate` API endpoint
  - Simplified from 80 lines of manual color theory to single API call
  - Supports 6 harmony types: monochromatic, analogous, complementary, split-complementary, triadic, tetradic
- Text Color Optimizer: Full implementation with WCAG compliance checking
  - Automatic black/white text color selection
  - Live preview with contrast ratios
  - AA/AAA compliance indicators
- Color Blindness Simulator: Fixed and working
  - Shows difference percentage for each simulation
  - Side-by-side comparison view
- Gradient Creator: Fixed to use correct API response structure
- Batch Operations: Fixed to extract output colors correctly

**UI Improvements:**
- Enable all accessibility tool cards (remove "Coming Soon" badges)
- Enable harmony palettes card
- Add safety check for gradient state to prevent undefined errors

All features now fully functional and properly integrated with Pastel API.

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

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

lib/api/client.ts

@@ -27,6 +27,8 @@ import type {
   NamedColorSearchData,
   HealthData,
   CapabilitiesData,
+  PaletteGenerateRequest,
+  PaletteGenerateData,
 } from './types';
 
 export class PastelAPIClient {
@@ -186,7 +188,7 @@ export class PastelAPIClient {
   }
 
   // Accessibility
-  async simulateColorblindness(request: ColorBlindnessRequest): Promise<ApiResponse<ColorBlindnessData>> {
+  async simulateColorBlindness(request: ColorBlindnessRequest): Promise<ApiResponse<ColorBlindnessData>> {
     return this.request<ColorBlindnessData>('/colors/colorblind', {
       method: 'POST',
       body: JSON.stringify(request),
@@ -226,6 +228,14 @@ export class PastelAPIClient {
       method: 'GET',
     });
   }
+
+  // Palette Generation
+  async generatePalette(request: PaletteGenerateRequest): Promise<ApiResponse<PaletteGenerateData>> {
+    return this.request<PaletteGenerateData>('/palettes/generate', {
+      method: 'POST',
+      body: JSON.stringify(request),
+    });
+  }
 }
 
 // Export singleton instance