Motivation

• Prevent sending invalid phone numbers to the server and improve UX by showing a local error before starting phone-number auth.

Description

• Added isPhoneNumberValid() in LoginFragment that uses libphonenumber to parse and validate the entered number.
• Blocked the initial start_phone_number_auth call in onNextClick when the number is invalid and show a localized toast using a new invalid_phone_number string resource.
• Added the invalid_phone_number entry to Houseclub/src/main/res/values/strings.xml.

Testing

• Ran ./gradlew :Houseclub:assembleDebug which failed in this environment because the Gradle wrapper script is not present. (failure)
• Ran gradle :Houseclub:assembleDebug which failed with Unsupported class file major version 69 due to a toolchain mismatch in the execution environment. (failure)

Codex Task