Tighten E.164 regex in regexes.ts to require a non-zero leading digit with 7-15 digits

[Cprakhar]

Summary

Tightened the E.164 regex to /^\+[1-9]\d{6,14}$/ to require a non-zero leading digit while keeping the 7–15 digit constraint. Added invalid test cases for leading-zero country codes and cleaned up the E.164 test harness logging.

Tests

pnpm test (reported passing) Added the below test cases

    "+0000000", // leading zero country code
    "+0123456789", // leading zero with more digits

Related PRs:

• #3476

Fixes: #5517