feat: Email Global Customization Page! 🎨

## 3. Email Global Customization

**Features:**
- Brand Colors (Primary & Secondary)
- Hero Card Gradient (Start & End colors)
- Button Styling (Text color)
- Logo & Branding (Logo URL, Header/Footer text)
- Live color previews
- Reset to defaults

**Settings:**
- `primary_color` - Primary buttons (#7f54b3)
- `secondary_color` - Outline buttons (#7f54b3)
- `hero_gradient_start` - Hero card gradient start (#667eea)
- `hero_gradient_end` - Hero card gradient end (#764ba2)
- `button_text_color` - Button text (#ffffff)
- `logo_url` - Store logo URL
- `header_text` - Email header text
- `footer_text` - Email footer text

**UI Features:**
- Color pickers with hex input
- Live gradient preview
- Live button preview
- Back navigation
- Reset to defaults button
- Save/loading states

**Navigation:**
- Added card to Notifications page
- Route: `/settings/notifications/email-customization`
- API: `/notifications/email-settings`

**Files:**
- `routes/Settings/Notifications.tsx` - Added card
- `routes/Settings/Notifications/EmailCustomization.tsx` - NEW
- `App.tsx` - Added route

Ready to apply these settings to email templates! 🚀

admin-spa/src/App.tsx

@@ -203,6 +203,7 @@ import SettingsLocalPickup from '@/routes/Settings/LocalPickup';
 import SettingsNotifications from '@/routes/Settings/Notifications';
 import StaffNotifications from '@/routes/Settings/Notifications/Staff';
 import CustomerNotifications from '@/routes/Settings/Notifications/Customer';
+import EmailCustomization from '@/routes/Settings/Notifications/EmailCustomization';
 import EditTemplate from '@/routes/Settings/Notifications/EditTemplate';
 import SettingsDeveloper from '@/routes/Settings/Developer';
 import MorePage from '@/routes/More';
@@ -493,6 +494,7 @@ function AppRoutes() {
       <Route path="/settings/notifications" element={<SettingsNotifications />} />
       <Route path="/settings/notifications/staff" element={<StaffNotifications />} />
       <Route path="/settings/notifications/customer" element={<CustomerNotifications />} />
+      <Route path="/settings/notifications/email-customization" element={<EmailCustomization />} />
       <Route path="/settings/notifications/edit-template" element={<EditTemplate />} />
       <Route path="/settings/brand" element={<SettingsIndex />} />
       <Route path="/settings/developer" element={<SettingsDeveloper />} />