Add ESP32 OTA firmware update with rollback confirmation.

Stream application binaries to the inactive OTA slot via POST /api/system/ota,
validate the esp_app_desc project name in core, and cancel rollback after a
healthy network boot through OtaService::confirmBoot().

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

Software/components/core/src/OtaAppDescriptor.cpp

@@ -0,0 +1,77 @@
+/**
+ * @file    OtaAppDescriptor.cpp
+ * @brief   OTA app descriptor validation implementation.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-07
+ */
+
+#include "core/OtaAppDescriptor.hpp"
+
+#include <cstring>
+#include <expected>
+
+namespace core {
+
+namespace {
+
+constexpr std::size_t kMinProjectNameCheck =
+    kOtaAppDescriptorOffset + 4U + 4U + 32U + 32U;
+
+[[nodiscard]] std::uint32_t readLe32(const std::uint8_t* p)
+{
+    return static_cast<std::uint32_t>(p[0])
+           | (static_cast<std::uint32_t>(p[1]) << 8)
+           | (static_cast<std::uint32_t>(p[2]) << 16)
+           | (static_cast<std::uint32_t>(p[3]) << 24);
+}
+
+[[nodiscard]] bool projectNameMatches(const char* field)
+{
+    return std::strncmp(field, kOtaProjectName, sizeof(kOtaProjectName) - 1U)
+           == 0;
+}
+
+} // namespace
+
+const char* otaImageErrorToken(OtaImageError error) noexcept
+{
+    switch (error) {
+    case OtaImageError::InsufficientHeader:
+        return "insufficient_header";
+    case OtaImageError::InvalidMagic:
+        return "invalid_magic";
+    case OtaImageError::InvalidProject:
+        return "invalid_project";
+    }
+    return "unknown";
+}
+
+std::expected<void, OtaImageError>
+validateOtaAppDescriptor(std::span<const std::uint8_t> imagePrefix)
+{
+    if (imagePrefix.size() < kMinProjectNameCheck) {
+        return std::unexpected(OtaImageError::InsufficientHeader);
+    }
+
+    const std::uint8_t* desc = imagePrefix.data() + kOtaAppDescriptorOffset;
+    const std::uint32_t magic = readLe32(desc);
+    if (magic != kOtaAppDescriptorMagic) {
+        return std::unexpected(OtaImageError::InvalidMagic);
+    }
+
+    const char* projectName =
+        reinterpret_cast<const char*>(desc + 4U + 4U + 32U);
+    if (!projectNameMatches(projectName)) {
+        return std::unexpected(OtaImageError::InvalidProject);
+    }
+
+    return {};
+}
+
+} // namespace core