This pull request makes phone numbers optional for both user registrations and bookings, and updates validation, database schema, and UI to reflect this change. The main focus is to ensure that users are no longer required to provide a phone number, and that the application gracefully handles cases where a phone number is absent.
**Database & Resource Model Updates**
* Made the `phone_number` attribute in the `users` table and the `customer_phone` attribute in the `bookings` table nullable, including migration and resource snapshot updates. [[1]](diffhunk://#diff-baa6aed3674c4d6cbbebeafb076662df02dc4c25231dbd9dc9c8f0534ed1a1bfR1-R29) [[2]](diffhunk://#diff-a401f66b2ae5bfb798eb1bc2221bfeeac943e258950c90d59570b0bae05d3664R1-R244) [[3]](diffhunk://#diff-0c1180d6f6abc19b5987c8703bdee9ef67905535202f950e8327c32bd5b89d8aR1-R82)
* Updated Ash resource definitions in `user.ex` and `booking.ex` to allow `phone_number` and `customer_phone` to be `nil`. [[1]](diffhunk://#diff-9194b9d80dce091f6dcb56f784217272ae160e35454c4b4ccc8850ad5ee06e38L152-R152) [[2]](diffhunk://#diff-4b1ddd6d86899f2144c69d142883b8719c755e32c03dbda5da2188208a5ad503L55-R55) [[3]](diffhunk://#diff-4b1ddd6d86899f2144c69d142883b8719c755e32c03dbda5da2188208a5ad503L170-R170)
**Validation & Parsing Logic**
* Renamed and refactored user registration field validation to `ParseRegistrationFields`, allowing phone numbers to be omitted and trimming input values. Empty phone numbers are now treated as absent rather than as errors. [[1]](diffhunk://#diff-8ffdd76e260e3cda6f0816c8e585ae76b993a90d2519c38185a5fe22b4b49e47L1-R1) [[2]](diffhunk://#diff-8ffdd76e260e3cda6f0816c8e585ae76b993a90d2519c38185a5fe22b4b49e47R14-R60)
* Updated the authentication callback logic to trim input values and omit the phone number parameter if it is blank.
**User Interface Improvements**
* Updated registration and booking forms to indicate that phone numbers are optional, removed the required attribute, and improved placeholder text. [[1]](diffhunk://#diff-f356eb84970d8c9ee6ff1992c297b0cae07bade37ff967c1e6e0de6f8b67081cL101-R115) [[2]](diffhunk://#diff-43c0e1f7a869ee5c43a911bc10dc80cbb265a8672340ef0fa7c1d3009c047f02L92-R92)
* Updated email templates and confirmation screens to display "N/A" or "-" when phone numbers are missing. [[1]](diffhunk://#diff-48468ef2d1bb2c33b5ffb40457b77532815c7faf1830932661f665bff58b2177R6-R11) [[2]](diffhunk://#diff-3f33187b4021450b481ce53fe13166addea582c627f2cfbc99c75c7ce5c34857L10-R10) [[3]](diffhunk://#diff-43c0e1f7a869ee5c43a911bc10dc80cbb265a8672340ef0fa7c1d3009c047f02L92-R92)
**Profile Management**
* Improved profile update flow to ensure the form reflects the latest user data after saving changes.
* Made the "Full Name" field explicitly required in the profile form UI.
