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-sigmastudio.tex

@@ -21,9 +21,18 @@ the program, not to drive the chip in operation.
 The whole program can be built and exported offline, without a physical
 ADAU1701 or a USBi programmer connected. A USBi block is placed in the
 Hardware Configuration only because SigmaStudio requires a communication
-channel to compile; it is never used for a real download in this project.
+channel to compile.
 \end{drkey}
 
+\begin{drref}[Live connection is also possible]
+Since firmware~0.9.0, DigiRadio's \texttt{net::SigmaStudioTcpServer}
+(Chapter~\ref{ch:adau1701}, Section~\ref{sec:adau1701-sigmastudio-tcp})
+exposes a TCP:8086 bridge so SigmaStudio can \emph{Connect} and
+\emph{Link Compile Download} directly against a running board, for live DSP
+tuning and bench debugging. The export-only workflow below remains the
+simplest path for ordinary firmware builds.
+\end{drref}
+
 \section{Hardware Configuration}
 \label{sec:ss-hwcfg}
 
@@ -270,9 +279,11 @@ The firmware's ADAU1701 driver replays the program data over
 I\textsuperscript{2}C at boot, and uses the parameter addresses for
 safeload updates.
 
-\begin{drnote}[No download needed]
-Since there is no ADAU1701 attached during development, do \emph{not} use
-\emph{Link Compile Download} (it would fail trying to reach the chip).
-\emph{Export System Files} compiles the schematic and writes the files
-directly.
+\begin{drnote}[Export System Files vs. Link Compile Download]
+Without a physical ADAU1701/USBi attached, \emph{Export System Files} is what
+you want: it compiles the schematic and writes the files directly, with no
+chip connection required. \emph{Link Compile Download} instead needs a live
+communication channel to a chip --- either the classic USBi/ICP dongle, or
+DigiRadio's own TCP:8086 SigmaStudio bridge (Section~\ref{sec:adau1701-sigmastudio-tcp})
+when connecting live to a running board.
 \end{drnote}