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-hardware.tex

@@ -132,7 +132,7 @@ in the module's own non-volatile memory.
 \begin{drcaution}[I\textsuperscript{2}S slave mode]
 The PCB routes ADAU1701 \texttt{SDATA\_OUT0} to the module over
 I\textsuperscript{2}S (BCLK, LRCLK, PCM data). Firmware must initialise
-\texttt{AT+AUXCFG=3} and \texttt{AT+I2SCFG=67}, not Line-In
+\texttt{AT+AUXCFG=3} and \texttt{AT+I2SCFG=35}, not Line-In
 (\texttt{AT+AUXCFG=1}). See Chapter~\ref{ch:bt1035}, Section~\ref{sec:bt1035-i2s}.
 \end{drcaution}
 
@@ -525,7 +525,7 @@ ever used.}
     \midrule
     UART with flow control & TX/RX + RTS/CTS wired            & verified \\
     I\textsuperscript{2}S init (firmware) &
-      \texttt{AT+AUXCFG=3}, \texttt{AT+I2SCFG=67} & driver rule \\
+      \texttt{AT+AUXCFG=3}, \texttt{AT+I2SCFG=35} & driver rule \\
     I\textsuperscript{2}S input & receives clocks from ADAU master (slave) & verified \\
     Reset line             & RESET (GPIO17) driven by ESP32    & verified \\
     \bottomrule