Add mobile-friendly browser phone shortcode for frontend use

- Created TWP_Shortcodes class with [twp_browser_phone] shortcode
- Mobile-first responsive CSS design with touch-friendly interface
- Frontend JavaScript integration with Twilio Voice SDK v2
- Permission checks for logged-in users with twp_access_browser_phone capability
- Haptic feedback and dark mode support
- Configurable shortcode parameters (title, show_title, compact)
- Updated plugin version to 2.1.0 in main file
- Added comprehensive documentation to README.md

Features:
- Visual dialpad with DTMF support
- Real-time connection status indicators
- Call timer and queue management
- Auto-scaling for mobile devices (320px+)
- Optimized for both desktop and mobile use

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

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

README.md

@@ -46,13 +46,15 @@ This plugin **requires** the Twilio PHP SDK v8.7.0 to function. The plugin will
 - **Queue Notifications**: SMS alerts to designated numbers when calls enter queues
 
 ### 🌐 Browser Phone (WebRTC)
-- **In-Browser Calling**: Make and receive calls directly from WordPress admin
+- **In-Browser Calling**: Make and receive calls directly from WordPress admin or frontend
 - **Twilio Voice SDK v2**: Uses latest SDK for WebRTC functionality
 - **Visual Dialpad**: Click-to-dial interface with DTMF support
 - **Call Controls**: Mute, hold indicators, call timer
 - **Auto-Answer**: Optional automatic call acceptance
 - **Queue Integration**: Accept calls from specific queues
 - **Token Management**: Automatic token refresh for uninterrupted service
+- **Mobile-Friendly**: Responsive design optimized for smartphones and tablets
+- **Shortcode Support**: Embed browser phone on any page with `[twp_browser_phone]`
 
 ### 🕒 Business Hours Management
 - **Schedule-based Routing**: Different call flows for business hours vs after-hours
@@ -258,6 +260,38 @@ This plugin **requires** the Twilio PHP SDK v8.7.0 to function. The plugin will
    - **Queue Timeouts**: Alert when calls wait too long (configurable threshold)
    - **Missed Calls**: Alert when calls are abandoned or timeout
 
+## Frontend Browser Phone
+
+### Shortcode Usage
+The browser phone can be embedded on any WordPress page using the `[twp_browser_phone]` shortcode. This is perfect for creating dedicated agent pages or customer service portals.
+
+**Basic Usage:**
+```
+[twp_browser_phone]
+```
+
+**With Options:**
+```
+[twp_browser_phone title="Customer Service Phone" show_title="true" compact="false"]
+```
+
+### Shortcode Parameters
+- **title**: Custom title for the phone widget (default: "Browser Phone")
+- **show_title**: Display the title above the phone (default: "true")
+- **compact**: Use compact layout for smaller spaces (default: "false")
+
+### Permission Requirements
+- Users must be **logged in** to access the browser phone
+- Users need the **`twp_access_browser_phone`** capability or **`manage_options`**
+- Phone Agent role users have access by default
+
+### Mobile Optimization
+- **Responsive Design**: Adapts to all screen sizes
+- **Touch-Friendly**: Large buttons optimized for mobile devices
+- **Haptic Feedback**: Vibration on button press (where supported)
+- **Auto-Zoom Prevention**: Proper viewport handling for mobile browsers
+- **Dark Mode Support**: Automatically adapts to user's system preference
+
 ## Voice Configuration
 
 ### ElevenLabs Integration