PHONE DISPLAY MANAGER v2

Default login:
username: admin
password: admin123

NEW:
- Bulk price removed.
- Compatible model now has its own brand_id.
- One display can be compatible with models from ANY brand.
- Example: OPPO display -> Realme 8, Realme 9, Vivo Y...
- Compatible model has brand + typed model name.
- Change Password page included.

NEW INSTALL:
Import schema.sql into a NEW database.

UPGRADE EXISTING DATABASE:
1. Backup database.
2. Import migrate_existing.sql.
3. If the old products table does not have bulk_price, remove that ALTER statement.
4. Existing compatibility records are initially assigned the display's own brand. Edit them afterward where cross-brand compatibility applies.

Requirements: PHP 8+, MySQL/MariaDB, mysqli.
