48 kHz only: drop 96 kHz from the AES67 output

All sources (player, test signals) are 48 kHz; at 96 kHz Spotify and HLS
played at the wrong speed. Validation, the page and the docs allow 48000
only, and a 96000 stored before is reset to 48000 at boot (stored values
aren't re-validated, and the SDP would still have said 96 kHz).

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

docs/user-guide.md

@@ -105,7 +105,7 @@ The secret is write-only: after saving, the field shows empty. Leave it empty to
 | Channels | 2 | 1 or 2. |
 | Mono sum | off | Sends (left + right) / 2 as a 1-channel stream. Forces *Channels* to 1; it can't clip. |
 | Bit depth | L24 | L24 or L16. |
-| Sample rate | 48000 | **Use 48000 with Spotify and HLS** (see [Limitations](#limitations)). |
+| Sample rate | 48000 | Fixed; all sources are 48 kHz. |
 | Packet time | 1 ms | 0.125, 0.25, 0.333, 1 or 4 ms. 1 ms is the AES67 default and works with nearly all receivers. |
 | Payload type / SSRC / time stamp offset | 96 / 0 / 0 | Only change these if a receiver needs it. |
 
@@ -220,7 +220,6 @@ The full device API (status, config, SDP, firmware) is described in `docs/aes67-
 ## Limitations
 
 These are known limitations in the current firmware:
-- **96 kHz:** only the test tone and pink noise work correctly at 96 kHz. Spotify and HLS are 48 kHz sources and must be streamed at **48000**. At 96 kHz they play at the wrong speed.
 - **Autoplay stream on boot:** the checkbox has no effect yet. HLS always starts on boot.
 - **VLAN split** (separate VLANs for AES67 and internet) isn't available yet.
 - **No password** on the web page or API.