Add internet radio streaming with runtime API, modernize web UI, remove auto-tune/beep at boot

Streaming (main feature this session):
- New WebRadioConfig/WebRadioJson core types, ISecureStore-backed persistence
- New webradio::WebRadioService (thread-safe live config) + GET/POST /api/streaming
- web_radio_stream task now runtime-toggleable (no reboot), no hardcoded URL
- Content-Type diagnostic: warns clearly when a URL is a webpage, not an audio stream

Boot cleanup:
- Removed boot-time auto FM/DAB tune, auto-beep, and the (now-concluded) Si4684
  crystal IBIAS/CTUN empirical sweep from main.cpp — tuning/beep are on-demand
  via the existing REST API only

Web UI:
- Modernized styling (cards, gradients, toggle switches, light/dark theme)
- New Stream tab wired to /api/streaming

Fixes found via real idf.py build (not just clangd):
- Restored wrongly-removed si4684/Si4684Tuner.hpp include in main.cpp
- Fixed MP3Decode() argument types in web_radio_stream.cpp (unsigned char**/int*)

Quality-gate fixes:
- Host-test stub headers (esp_log.h, freertos/*) so TunerService.cpp's
  scanForStation logging/pacing compiles for station_service_test /
  integration_service_test instead of running stale binaries
- Added WifiScanner and WebRadioService manual sections; filled in missing
  Doxygen docs on BluetoothService, i2s_sdata_probe, test_firmware, Bt1035At
- Ignore clangd's .cache/ index directory

Also includes prior uncommitted work carried in the tree: Wi-Fi/Bluetooth
device scan REST API and UI (WifiScanner, BT scan), SigmaStudio TCP bridge,
and the current ADAU1701 SigmaStudio DSP program export.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Software/docs/manual/ch-firmware.tex

@@ -151,7 +151,7 @@ safeload registers.
 \paragraph{FSC-BT1035 (Bluetooth).}
 The module is controlled by AT commands over UART with hardware flow control.
 The initialisation sequence includes enabling I\textsuperscript{2}S slave mode
-(\texttt{AT+AUXCFG=3} and \texttt{AT+I2SCFG=67}), which is required for the
+(\texttt{AT+AUXCFG=3} and \texttt{AT+I2SCFG=35}), which is required for the
 wired digital audio path from the ADAU1701 to the module.
 Command responses are parsed explicitly, with timeouts treated as errors.
 Full driver API, boot flow, and error codes are in Chapter~\ref{ch:bt1035}.
@@ -218,7 +218,7 @@ bring-up:
     defaults) via ADAU1701 safeload before network bring-up.
   \item \textbf{FSC-BT1035} (UART): \texttt{bt1035::Bt1035Driver::boot()}
     enables I\textsuperscript{2}S slave mode (\texttt{AT+AUXCFG=3},
-    \texttt{AT+I2SCFG=67}) after the DSP path is configured
+    \texttt{AT+I2SCFG=35}) after the DSP path is configured
     (Chapter~\ref{ch:bt1035}).
 \end{enumerate}