[alias-server] add copyright header to lint

Summary:
T3060

Add copyright header to all files and ensure it is present with linting

Test Plan:
Review copyright header for appropriateness
Confirm only changes are adding these commented lines to the top of every file

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13587