Relicense project under the GNU Affero General Public License v3 (AGPLv3)

and add the Enterprise / Commercial licensing option.

Main changes:
- Replace GPLv3 headers with AGPLv3 headers in source files.
- Update LICENSE file to the full AGPLv3 text.
- Add ENTERPRISE.md describing the dual-licensing model:
  * Community Edition: AGPLv3 (strong copyleft, including network use).
  * Enterprise / Commercial Edition: proprietary license for production /
    multi-user / OEM use without the obligation to disclose derivative code.
- Update README with a new "License and Commercial Use" section pointing to
  ENTERPRISE.md and clarifying how companies can obtain a commercial license.

Why this change:
- AGPLv3 ensures that modified versions offered as a service or deployed
  in production environments must provide corresponding source code.
- The Enterprise / Commercial edition provides organizations with an
  alternative proprietary license that allows internal, large-scale, or OEM
  use (bulk provisioning, policy enforcement, inventory / revocation,
  custom attestation, signed builds) without AGPL disclosure obligations.

This commit formally marks the first release that is dual-licensed:
AGPLv3 for the Community Edition and a proprietary commercial license
for Enterprise customers.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

src/fido/cbor_make_credential.c

@@ -3,16 +3,16 @@
  * Copyright (c) 2022 Pol Henarejos.
  *
  * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
+ * it under the terms of the GNU Affero General Public License as published by
  * the Free Software Foundation, version 3.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
+ * Affero General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
  */
 
 #include "cbor_make_credential.h"