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/core/test/host_stubs/esp_log.h

@@ -0,0 +1,21 @@
+/**
+ * @file    esp_log.h
+ * @brief   Host-test stand-in for ESP-IDF logging macros.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Not shipped to device firmware: idf.py builds resolve the real ESP-IDF
+ * esp_log.h first. Only used so services/tuner/src/TunerService.cpp — which
+ * logs scan progress on real hardware — can also compile against
+ * components/core/test host tests without pulling in ESP-IDF.
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#define ESP_LOGE(tag, fmt, ...) ((void)0)
+#define ESP_LOGW(tag, fmt, ...) ((void)0)
+#define ESP_LOGI(tag, fmt, ...) ((void)0)
+#define ESP_LOGD(tag, fmt, ...) ((void)0)
+#define ESP_LOGV(tag, fmt, ...) ((void)0)

Software/components/core/test/host_stubs/freertos/FreeRTOS.h

@@ -0,0 +1,19 @@
+/**
+ * @file    FreeRTOS.h
+ * @brief   Host-test stand-in for the FreeRTOS core header.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Not shipped to device firmware: idf.py builds resolve the real FreeRTOS
+ * headers first. Only used so services/tuner/src/TunerService.cpp — which
+ * paces scan steps with vTaskDelay on real hardware — can also compile
+ * against components/core/test host tests without pulling in FreeRTOS.
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+using TickType_t = unsigned int;
+
+#define pdMS_TO_TICKS(ms) (static_cast<TickType_t>(ms))

Software/components/core/test/host_stubs/freertos/task.h

@@ -0,0 +1,18 @@
+/**
+ * @file    task.h
+ * @brief   Host-test stand-in for the FreeRTOS task API.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Not shipped to device firmware: idf.py builds resolve the real FreeRTOS
+ * headers first. vTaskDelay is a no-op here — host tests assert scan logic
+ * against a FakeTuner, not real hardware settle timing.
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#include "freertos/FreeRTOS.h"
+
+inline void vTaskDelay(TickType_t) {}