Add booking system with calendar and email notifications (v0.3.0)

- Booking Custom Post Type with full management features
- Room and guest relationship tracking
- Check-in/check-out date management with validation
- Booking status workflow (pending, confirmed, checked_in, checked_out, cancelled)
- Automatic price calculation using existing Calculator
- Availability system with real-time conflict detection
- AJAX endpoint for instant availability validation
- Calendar admin page with monthly view and room/building filters
- Color-coded booking status display with legend
- Email notifications for new bookings, confirmations, and cancellations
- HTML email templates with placeholder-based system
- Auto-generated booking references (BNB-YYYY-NNNNN)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -207,10 +207,15 @@ wp-bnb/
 ├── src/                    # PHP source code (PSR-4: Magdev\WpBnb)
 │   ├── Plugin.php          # Main plugin singleton
 │   ├── Admin/              # Admin pages
+│   │   ├── Calendar.php    # Availability calendar page
 │   │   └── Seasons.php     # Seasons management page
+│   ├── Booking/            # Booking system
+│   │   ├── Availability.php # Availability checking
+│   │   └── EmailNotifier.php # Email notifications
 │   ├── License/
 │   │   └── Manager.php     # License management
 │   ├── PostTypes/          # Custom post types
+│   │   ├── Booking.php     # Booking post type
 │   │   ├── Building.php    # Building post type
 │   │   └── Room.php        # Room post type
 │   ├── Pricing/            # Pricing system
@@ -397,3 +402,69 @@ Admin features always work; frontend requires valid license.
 - Price modifiers as multipliers are more flexible than percentages
 - Calculator class separates concerns from post type class
 - Weekend days stored as comma-separated string in options
+
+### 2026-01-31 - Version 0.3.0 (Booking System)
+
+**Completed:**
+
+- Created `src/PostTypes/Booking.php` custom post type
+  - Room and guest relationship tracking
+  - Check-in/check-out date management with validation
+  - Status workflow (pending, confirmed, checked_in, checked_out, cancelled)
+  - Auto-generated booking references (BNB-YYYY-NNNNN)
+  - Four meta boxes: Room & Dates, Guest Info, Pricing, Status & Notes
+  - Conflict detection prevents double-booking
+  - Price calculation using existing Calculator class
+  - Admin columns with room, guest, dates, nights, price, status
+  - Filters by room and status
+  - Status badges with color coding
+- Created `src/Booking/Availability.php` class
+  - Real-time availability checking via AJAX
+  - Conflict detection algorithm
+  - Calendar data generation for rooms and buildings
+  - Utility methods for upcoming bookings, today's check-ins/outs
+- Created `src/Admin/Calendar.php` admin page
+  - Monthly calendar view with room/building filters
+  - Color-coded booking status display
+  - Month navigation (previous/next/today)
+  - Click-to-edit booking functionality
+  - Hover tooltips with booking details
+  - Legend for status colors
+- Created `src/Booking/EmailNotifier.php` class
+  - Admin notification for new bookings
+  - Guest confirmation email on booking confirmation
+  - Cancellation emails to guest and admin
+  - HTML email templates with inline styles
+  - Placeholder-based template system
+  - Filter hooks for customizing emails
+- Updated `src/Plugin.php`
+  - Registered Booking post type
+  - Initialized Calendar admin page
+  - Initialized EmailNotifier
+  - Added AJAX handler for availability checking
+  - Updated asset enqueuing for Booking screens
+- Updated `assets/js/admin.js`
+  - Booking form with AJAX availability checking
+  - Real-time nights display
+  - Price calculation and display
+  - Status preview update
+  - Date validation (check-out after check-in)
+  - Calendar page interactivity
+- Updated `assets/css/admin.css`
+  - Booking info display styles
+  - Availability status indicators
+  - Price breakdown styles
+  - Calendar grid and cell styles
+  - Legend and filter styles
+  - Responsive design for calendar
+- Updated version to 0.3.0
+
+**Learnings:**
+
+- Booking conflicts use overlap detection: `A.check_in < B.check_out AND A.check_out > B.check_in`
+- Excluding cancelled bookings from conflict checks allows rebooking same dates
+- Guest info stored in booking meta (Phase 4 will add separate Guest CPT)
+- AJAX availability check returns price calculation for immediate feedback
+- Calendar displays bookings color-coded by status for quick visual overview
+- HTML email templates with inline CSS for better email client compatibility
+- Status transitions can trigger different email notifications via hooks