Initial commit: MT firmware project

- BLE peripheral applications
- dr_piezo and bladder_patch projects

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

external/mbedtls/LICENSE

@@ -0,0 +1,5 @@
+Unless specifically indicated otherwise in a file, Mbed TLS files are provided
+under the Apache License 2.0, or the GNU General Public License v2.0 or later
+(SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later).
+
+A copy of these licenses can be found in apache-2.0.txt and gpl-2.0.txt