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/components/drivers/si4684/include/si4684/Si4684Driver.hpp

@@ -106,14 +106,21 @@ public:
      *           rail ramp before app_main runs.
      *
      * @dname    boot
-     * @param    band  DAB or FM application to load.
+     * @param    band       DAB or FM application to load.
+     * @param    xtalIbias  POWER_UP ARG3 IBIAS, 10 uA steps (AN649 §Command
+     *                      0x01); default matches the values already
+     *                      verified live (72 = 720 uA startup bias).
+     * @param    xtalCtun   POWER_UP ARG8 CTUN, 0-63 (AN649 §Command 0x01);
+     *                      default matches the values already verified live.
      * @return   Ok on success, or Si4684Error.
      * @pubstate writes booted_ and loadedBand_ on success.
      *
      * @author   Michele Bigi
      * @date     2026-07-06
      */
-    [[nodiscard]] std::expected<void, Si4684Error> boot(Si4684Band band);
+    [[nodiscard]] std::expected<void, Si4684Error> boot(
+        Si4684Band band, std::uint8_t xtalIbias = 72U,
+        std::uint8_t xtalCtun = 31U);
 
     /**
      * @brief    isBooted — query whether boot completed successfully.
@@ -387,7 +394,10 @@ private:
     [[nodiscard]] std::expected<void, Si4684Error> ensureBand(
         Si4684Band band) const;
     [[nodiscard]] std::expected<void, Si4684Error> waitCts();
-    [[nodiscard]] std::expected<void, Si4684Error> waitStc();
+    [[nodiscard]] std::expected<void, Si4684Error> waitStc(
+        int maxRetries = 250);
+    [[nodiscard]] std::expected<bool, Si4684Error> pollStc();
+    [[nodiscard]] std::expected<void, Si4684Error> clearFmStc();
     [[nodiscard]] std::expected<void, Si4684Error> sendCommand(
         std::span<const std::uint8_t> bytes);
     [[nodiscard]] std::expected<void, Si4684Error> readRaw(

Software/components/drivers/si4684/include/si4684/Si4684Tuner.hpp

@@ -190,10 +190,25 @@ private:
      */
     [[nodiscard]] static core::TunerError mapError(Si4684Error error) noexcept;
 
+    /**
+     * @brief    ensureBandLoaded — HOST_LOAD FM/DAB image when band differs.
+     *
+     * @dname    ensureBandLoaded
+     * @param    band  Required application band for the next operation.
+     * @return   Ok when the chip runs the requested image.
+     * @pubstate may reload firmware (~1 s) and stop an active DAB service.
+     *
+     * @author   Michele Bigi
+     * @date     2026-08-05
+     */
+    [[nodiscard]] std::expected<void, core::TunerError> ensureBandLoaded(
+        core::TunerBand band);
+
     Si4684Driver& driver_;
     std::uint8_t dabIndex_;
     core::FrequencyKHz fmFrequency_;
     std::uint8_t volume_;
+    bool fmBandReady_;
     core::RdsMetadataAccumulator rdsMetadata_;
     core::DabDynamicLabelAccumulator dabDynamicLabel_;
     std::optional<std::uint32_t> lastDabServiceId_;

Software/components/drivers/si4684/include/si4684/Si4684Types.hpp

@@ -18,6 +18,7 @@
 #include <array>
 #include <cstddef>
 #include <cstdint>
+#include <optional>
 #include <vector>
 
 namespace si4684 {
@@ -91,11 +92,11 @@ struct Si4684SysState {
  * @date     2026-07-06
  */
 struct Si4684FmRsq {
-    core::FrequencyKHz frequency; ///< Tuned centre frequency in kHz.
-    std::int8_t rssiDbuV;         ///< RSSI in dBµV.
-    std::int8_t snrDb;            ///< SNR in dB.
-    bool valid;                   ///< RSQ valid flag from the chip.
-    bool stereo;                  ///< Stereo pilot detected.
+    std::optional<core::FrequencyKHz> frequency; ///< READFREQ when in FM band.
+    std::int8_t rssiDbuV;                      ///< RSSI in dBµV.
+    std::int8_t snrDb;                         ///< SNR in dB.
+    bool valid;                                ///< RSQ valid flag from the chip.
+    bool stereo;                               ///< Stereo pilot detected.
 };
 
 /**