Feature: Add configurable default phone country calling code

[anonymoususer72041]

Summary

This pull request introduces support for a configurable default phone country calling code and updates phone number handling to normalize numbers to E.164 where possible.

The changes include:

Backend support for E.164 normalization

• Add StringUtility::extractPhoneNumberE164($string) to normalize phone numbers:
• Trims input and normalizes leading 00 to + (e.g. 0049... → +49...).
• Strips all non-digit characters except a leading +.
• If the input already starts with +, it is treated as an E.164-style number and returned as-is (after normalization).
• For local numbers without +, the default phone country calling code is applied and the number is converted to E.164.
• Update StringUtility::extractPhoneNumber($string) to delegate to extractPhoneNumberE164($string), while keeping the previous NANP-based implementation as commented legacy code for future refactoring.

Site configuration for default phone country calling code

• Add column default_phone_country_code (VARCHAR(8), default '+1') to the site table in the schema and schema migration.
• Extend the session and site configuration layer to store and retrieve the default phone country calling code (e.g. via Session::getDefaultPhoneCountryCode() / Session::setDefaultPhoneCountryCode() and Site::setDefaultPhoneCountryCode()).

Installer support (new installations)

• Extend the “Loading Extras – Localization” step in the installer to ask for the default phone country calling code.
• Add a + prefixed text input (defaultPhoneCountryCodeDigits) that only accepts digits on the client side.
• Store the chosen code as +<digits> in the site.default_phone_country_code column when the installer completes.
• Existing installations receive the new configuration column with a default of +1 as part of the schema migration and can then adjust it via the Admin UI.

Admin UI (Localization settings)

• Extend the Localization settings page to display and edit the default phone country calling code:
• Show only the digits part in the input field (e.g. +49 → 49).
• On save, clean the submitted value to digits only and persist it as +<digits> via Site::setDefaultPhoneCountryCode().
• If no digits are submitted, the existing value in the database is left unchanged.

Motivation

Historically, OpenCATS relied on a NANP-centric phone number format and hard-coded assumptions such as the country code +1. This causes several issues for non-US/Canadian users:

• Phone numbers entered in local formats for other countries are not consistently or correctly normalized.
• The system has no explicit notion of which country calling code should be applied when normalizing plain local numbers.
• Administrators outside the NANP region cannot configure their preferred default behavior centrally.

By introducing a configurable default phone country calling code and moving phone number handling toward E.164, this Pull Request:

• Makes phone number storage and processing more predictable and international-friendly.
• Allows each installation to set an appropriate default phone country calling code via:
• the installer for new installations, and
• the Localization settings in the Admin UI for existing installations.
• Keeps backward compatibility by:
• defaulting to +1 for existing databases (through the schema default),
• preserving the previous extractPhoneNumber() logic as commented legacy code to make a future refactor easier to understand,
• avoiding behavioral changes in the upgrade wizard flow (no new required steps during upgrade).

Overall, this is a first, backward-compatible step toward better internationalized phone number handling, while still fitting cleanly into existing OpenCATS patterns for configuration, schema updates, and settings UI.