Licences: MIT for the AES67 core and web page, GPL-3.0 for the rest

- LICENSE (GPL-3.0) at the root; an MIT LICENSE in each components/aes67_*
  and in web/, so they travel with the code when reused.
- THIRD_PARTY.md: third-party code and licences, and the known conflict of
  the Espressif binary audio libraries with GPL-3.0 (firmware contains cspot).
- CLAUDE.md: rule to keep GPL code out of the core; phase 2 item to replace
  the Espressif binaries (opencore-aacdec, Speex resampler).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/index.html

@@ -5,6 +5,7 @@
 <meta name="viewport" content="width=device-width,initial-scale=1">
 <title>AES67 device</title>
 <!--
+  SPDX-License-Identifier: MIT (see web/LICENSE)
   AES67 device web UI – reusable base.
   CORE  : status, PTP, AES67 output, network/VLAN, logging, SDP. Keep identical across projects.
   PROJECT: blocks between "PROJECT START/END" markers (HTML and the PROJECT object in the script).