Add Slice 5 ADAU1701 runtime audio control (firmware 0.5.0).

Safeload mixer/EQ/master on the ADAU1701, persist AudioProfile in NVS,
expose /api/audio routes and web UI controls, with host tests and manual sync.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/secure_store/CMakeLists.txt

@@ -1,5 +1,7 @@
 idf_component_register(
-    SRCS "src/NvsSecureStore.cpp"
+    SRCS
+        "src/NvsSecureStore.cpp"
+        "src/NvsAudioProfileStore.cpp"
     INCLUDE_DIRS "include"
     REQUIRES core nvs_flash
 )

Software/components/secure_store/include/secure_store/NvsAudioProfileStore.hpp

@@ -0,0 +1,42 @@
+/**
+ * @file    NvsAudioProfileStore.hpp
+ * @brief   NVS-backed IAudioProfileStore for user audio settings.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-06
+ */
+#pragma once
+
+#include "core/IAudioProfileStore.hpp"
+
+namespace secure_store {
+
+/**
+ * @brief    NvsAudioProfileStore — persists AudioProfile JSON in NVS.
+ *
+ * @dname    NvsAudioProfileStore
+ * @return   n/a (type)
+ * @pubstate Uses namespace digiradio, key audio_profile_json.
+ *
+ * @author   Michele Bigi
+ * @date     2026-07-06
+ */
+class NvsAudioProfileStore final : public core::IAudioProfileStore {
+public:
+    [[nodiscard]] bool hasProfile() const override;
+
+    [[nodiscard]] std::expected<void, core::StoreError> saveProfile(
+        const core::AudioProfile& profile) override;
+
+    [[nodiscard]] std::expected<core::AudioProfile, core::StoreError>
+    loadProfile() const override;
+
+    [[nodiscard]] std::expected<void, core::StoreError> clearProfile() override;
+};
+
+} // namespace secure_store

Software/components/secure_store/src/NvsAudioProfileStore.cpp

@@ -0,0 +1,111 @@
+/**
+ * @file    NvsAudioProfileStore.cpp
+ * @brief   NvsAudioProfileStore implementation.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-06
+ */
+
+#include "secure_store/NvsAudioProfileStore.hpp"
+
+#include "core/AudioProfileJson.hpp"
+
+#include "nvs.h"
+
+#include <string>
+#include <vector>
+
+namespace secure_store {
+
+namespace {
+constexpr char kNamespace[] = "digiradio";
+constexpr char kProfileKey[] = "audio_profile_json";
+} // namespace
+
+bool NvsAudioProfileStore::hasProfile() const
+{
+    nvs_handle_t handle = 0;
+    if (nvs_open(kNamespace, NVS_READONLY, &handle) != ESP_OK) {
+        return false;
+    }
+
+    std::size_t len = 0;
+    const esp_err_t err = nvs_get_str(handle, kProfileKey, nullptr, &len);
+    nvs_close(handle);
+    return err == ESP_OK && len > 1U;
+}
+
+std::expected<void, core::StoreError> NvsAudioProfileStore::saveProfile(
+    const core::AudioProfile& profile)
+{
+    const std::string json = core::serializeAudioProfileJson(profile);
+
+    nvs_handle_t handle = 0;
+    if (nvs_open(kNamespace, NVS_READWRITE, &handle) != ESP_OK) {
+        return std::unexpected(core::StoreError::IoFailed);
+    }
+
+    esp_err_t err = nvs_set_str(handle, kProfileKey, json.c_str());
+    if (err == ESP_OK) {
+        err = nvs_commit(handle);
+    }
+    nvs_close(handle);
+
+    if (err != ESP_OK) {
+        return std::unexpected(core::StoreError::IoFailed);
+    }
+    return {};
+}
+
+std::expected<core::AudioProfile, core::StoreError>
+NvsAudioProfileStore::loadProfile() const
+{
+    nvs_handle_t handle = 0;
+    if (nvs_open(kNamespace, NVS_READONLY, &handle) != ESP_OK) {
+        return std::unexpected(core::StoreError::NotFound);
+    }
+
+    std::size_t len = 0;
+    if (nvs_get_str(handle, kProfileKey, nullptr, &len) != ESP_OK || len == 0U) {
+        nvs_close(handle);
+        return std::unexpected(core::StoreError::NotFound);
+    }
+
+    std::vector<char> buf(len);
+    if (nvs_get_str(handle, kProfileKey, buf.data(), &len) != ESP_OK) {
+        nvs_close(handle);
+        return std::unexpected(core::StoreError::IoFailed);
+    }
+    nvs_close(handle);
+
+    if (auto parsed = core::parseAudioProfileJson(buf.data()); parsed) {
+        return *parsed;
+    }
+    return std::unexpected(core::StoreError::InvalidData);
+}
+
+std::expected<void, core::StoreError> NvsAudioProfileStore::clearProfile()
+{
+    nvs_handle_t handle = 0;
+    if (nvs_open(kNamespace, NVS_READWRITE, &handle) != ESP_OK) {
+        return std::unexpected(core::StoreError::IoFailed);
+    }
+
+    esp_err_t err = nvs_erase_key(handle, kProfileKey);
+    if (err == ESP_OK || err == ESP_ERR_NVS_NOT_FOUND) {
+        err = nvs_commit(handle);
+    }
+    nvs_close(handle);
+
+    if (err != ESP_OK) {
+        return std::unexpected(core::StoreError::IoFailed);
+    }
+    return {};
+}
+
+} // namespace secure_store