Implement Phase 7: Contact Form 7 Integration (v0.7.0)

Add custom CF7 form tags for booking requests:
- [bnb_building_select] - Building filter dropdown
- [bnb_room_select] - Room selection with capacity data
- [bnb_date_checkin/checkout] - Date pickers with validation
- [bnb_guests] - Guest count with capacity limits

Features:
- Server-side validation for all fields
- Real-time AJAX availability checking
- Automatic price calculation display
- Booking creation on form submission
- Guest record creation/linking
- Custom mail tags for CF7 templates

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

CHANGELOG.md

@@ -5,6 +5,51 @@ 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).
 
+## [0.7.0] - 2026-02-03
+
+### Added
+
+- Contact Form 7 Integration:
+  - New `src/Integration/CF7.php` class for CF7 integration
+  - Custom form tags: `[bnb_building_select]`, `[bnb_room_select]`, `[bnb_date_checkin]`, `[bnb_date_checkout]`, `[bnb_guests]`
+  - Server-side validation for all custom tags
+  - Availability checking before form submission
+  - Automatic booking creation on form submission with 'pending' status
+  - Guest record creation/linking using existing `find_or_create_guest` pattern
+  - Price calculation using existing Calculator class
+  - Email notifications via existing EmailNotifier
+- CF7 Frontend Assets:
+  - `assets/js/cf7-integration.js` for dynamic form behavior
+  - Building-based room filtering
+  - Date linking (checkout min = checkin + 1)
+  - Capacity validation against selected room
+  - AJAX availability checking with status display
+  - Dynamic price calculation display
+  - `assets/css/cf7-integration.css` for form styling
+  - Availability status indicators (checking/available/unavailable)
+  - Price display formatting
+  - Capacity warning styling
+  - Responsive design with dark mode support
+- Custom CF7 Mail Tags:
+  - `[_bnb_booking_reference]` - Generated booking reference
+  - `[_bnb_booking_id]` - Booking post ID
+  - `[_bnb_room_name]` - Selected room title
+  - `[_bnb_calculated_price]` - Formatted price
+  - `[_bnb_nights]` - Number of nights
+- Form Type Detection:
+  - Auto-detects booking forms by presence of `[bnb_room_select]`, `[bnb_date_checkin]`, `[bnb_date_checkout]`
+  - CSS class `wp-bnb-booking-form` for explicit form type declaration
+  - Inquiry forms use default CF7 email handling without booking creation
+
+### Changed
+
+- Plugin.php updated to conditionally initialize CF7 integration when CF7 is active
+- Frontend assets now include CF7-specific CSS and JavaScript when CF7 is detected
+
+### Dependencies
+
+- Contact Form 7 plugin required for CF7 integration features (optional)
+
 ## [0.6.1] - 2026-02-03
 
 ### Added