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>

CHANGELOG.md

@@ -5,6 +5,73 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.0] - 2026-01-31
+
+### Added
+
+- Booking System with full management features:
+  - Custom Post Type: Bookings (`bnb_booking`)
+  - Room and guest relationship tracking
+  - Check-in/check-out date management
+  - Booking status workflow (pending, confirmed, checked_in, checked_out, cancelled)
+  - Status transitions with validation
+  - Automatic price calculation using existing Calculator
+  - Price override option for manual adjustments
+  - Guest information storage (name, email, phone, notes)
+  - Guest count tracking (adults, children)
+  - Internal notes field for staff
+  - Auto-generated booking references (BNB-YYYY-NNNNN)
+- Availability System (`src/Booking/Availability.php`)
+  - Real-time availability checking
+  - Conflict detection for overlapping bookings
+  - AJAX endpoint for instant availability validation
+  - Calendar data generation for rooms and buildings
+  - Support for excluding booking from conflict check (for editing)
+  - Utility methods: get upcoming bookings, current bookings, today's check-ins/outs
+- Calendar Admin Page (WP BnB > Calendar)
+  - Monthly calendar view with availability visualization
+  - Room and building filter dropdowns
+  - Color-coded booking status display
+  - Month navigation (previous/next/today)
+  - Click-to-edit booking functionality
+  - Hover tooltips with booking details
+  - Legend for status colors
+  - Single room and multi-room views
+- Email Notifications (`src/Booking/EmailNotifier.php`)
+  - Admin notification for new bookings
+  - Guest confirmation email on booking confirmation
+  - Admin notification on booking confirmation
+  - Cancellation emails to guest and admin
+  - HTML email templates with styling
+  - Placeholder-based template system
+  - Filter hooks for customizing recipients, subject, and content
+- Booking Admin List Enhancements
+  - Custom columns: room, guest, dates, nights, price, status
+  - Status badges with color coding
+  - Filter by room and status
+  - Sortable columns for dates, guest, status
+  - Price override indicator
+- Booking Meta Boxes
+  - Room & Dates: room selection, date pickers, nights display, availability check
+  - Guest Information: contact details, guest count, notes
+  - Pricing: calculated price, breakdown display, recalculate button, override
+  - Status & Notes: status dropdown with preview, internal notes
+
+### Changed
+
+- Plugin.php enhanced with AJAX handlers and component initialization
+- Admin JavaScript updated with booking form functionality
+- Admin CSS updated with booking and calendar styles
+- Asset enqueuing now includes Booking post type screens
+
+### Security
+
+- Conflict detection prevents double-booking
+- Date validation ensures check-out is after check-in
+- Status transition validation prevents invalid state changes
+- Nonce verification on availability AJAX requests
+- Capability checks on all booking operations
+
 ## [0.2.0] - 2026-01-31
 
 ### Added
@@ -124,6 +191,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Input sanitization and output escaping
 - Server secret masking in license settings
 
+[0.3.0]: https://src.bundespruefstelle.ch/magdev/wp-bnb/releases/tag/v0.3.0
 [0.2.0]: https://src.bundespruefstelle.ch/magdev/wp-bnb/releases/tag/v0.2.0
 [0.1.0]: https://src.bundespruefstelle.ch/magdev/wp-bnb/releases/tag/v0.1.0
 [0.0.1]: https://src.bundespruefstelle.ch/magdev/wp-bnb/releases/tag/v0.0.1