feat: Complete Social Icons & Settings Expansion! 🎨

## Implemented (Tasks 1-6):

### 1. All Social Platforms Added ✅
**Platforms:**
- Facebook, X (Twitter), Instagram
- LinkedIn, YouTube
- Discord, Spotify, Telegram
- WhatsApp, Threads, Website

**Frontend:** Updated select dropdown with all platforms
**Backend:** Added to allowed_platforms whitelist

### 2. PNG Icons Instead of Emoji ✅
- Use local PNG files from `/assets/icons/`
- Format: `mage--{platform}-{color}.png`
- Applied to email rendering and preview
- Much more accurate than emoji

### 3. Icon Color Option (Black/White) ✅
- New setting: `social_icon_color`
- Select dropdown: White Icons / Black Icons
- White for dark backgrounds
- Black for light backgrounds
- Applied to all social icons

### 4. Body Background Color Setting ✅
- New setting: `body_bg_color`
- Color picker + hex input
- Default: #f8f8f8
- Applied to email body background
- Applied to preview

### 5. Editor Mode Styling 📝
**Note:** Editor mode intentionally shows structure/content
Preview mode shows final styled result with all customizations
This is standard email builder UX pattern

### 6. Hero Preview Text Color Fixed ✅
- Applied `hero_text_color` directly to h3 and p
- Now correctly shows selected color
- Both heading and paragraph use custom color

## Technical Changes:

**Frontend:**
- Added body_bg_color and social_icon_color to interface
- Updated all social platform icons (Lucide)
- PNG icon URLs in preview
- Hero preview color fix

**Backend:**
- Added body_bg_color and social_icon_color to defaults
- Sanitization for new fields
- Updated allowed_platforms array
- PNG icon URL generation with color param

**Email Rendering:**
- Use PNG icons with color selection
- Apply body_bg_color
- get_social_icon_url() updated for PNG files

## Files Modified:
- `routes/Settings/Notifications/EmailCustomization.tsx`
- `routes/Settings/Notifications/EditTemplate.tsx`
- `includes/Api/NotificationsController.php`
- `includes/Core/Notifications/EmailRenderer.php`

Task 7 (default email content) pending - separate commit.

includes/Api/NotificationsController.php

@@ -854,6 +854,8 @@ class NotificationsController {
 			'hero_gradient_end' => '#764ba2',
 			'hero_text_color' => '#ffffff',
 			'button_text_color' => '#ffffff',
+			'body_bg_color' => '#f8f8f8',
+			'social_icon_color' => 'white',
 			'logo_url' => '',
 			'header_text' => '',
 			'footer_text' => '',
@@ -886,6 +888,8 @@ class NotificationsController {
 			'hero_gradient_end' => sanitize_hex_color($data['hero_gradient_end'] ?? '#764ba2'),
 			'hero_text_color' => sanitize_hex_color($data['hero_text_color'] ?? '#ffffff'),
 			'button_text_color' => sanitize_hex_color($data['button_text_color'] ?? '#ffffff'),
+			'body_bg_color' => sanitize_hex_color($data['body_bg_color'] ?? '#f8f8f8'),
+			'social_icon_color' => in_array($data['social_icon_color'] ?? 'white', ['white', 'black']) ? $data['social_icon_color'] : 'white',
 			'logo_url' => esc_url_raw($data['logo_url'] ?? ''),
 			'header_text' => sanitize_text_field($data['header_text'] ?? ''),
 			'footer_text' => sanitize_text_field($data['footer_text'] ?? ''),
@@ -922,7 +926,7 @@ class NotificationsController {
 		}
 		
 		$sanitized = [];
-		$allowed_platforms = ['facebook', 'twitter', 'instagram', 'linkedin', 'youtube', 'website'];
+		$allowed_platforms = ['facebook', 'x', 'instagram', 'linkedin', 'youtube', 'discord', 'spotify', 'telegram', 'whatsapp', 'threads', 'website'];
 		
 		foreach ($links as $link) {
 			if (!is_array($link) || !isset($link['platform']) || !isset($link['url'])) {