2.1 Configuration POCOs (Mqtt, Storage, UrlFetch, ApiKey)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/FrameProcessor/Configuration/ApiKeyOptions.cs

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+using System.ComponentModel.DataAnnotations;
+using FrameProcessor.Domain;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Wraps the shared API key from <c>appsettings.json</c>. The configured value is bound
+/// from the top-level <c>ApiKey</c> key (which is a plain string in the JSON schema —
+/// see SPEC.md §6.1) into <see cref="Value"/>; consumers should call <see cref="ToApiKey"/>
+/// to obtain the constant-time-comparing <see cref="ApiKey"/> value type.
+/// </summary>
+public sealed class ApiKeyOptions
+{
+    public const string SectionName = "ApiKey";
+
+    [Required(AllowEmptyStrings = false)]
+    public string Value { get; set; } = string.Empty;
+
+    public ApiKey ToApiKey() => new(Value);
+}

src/FrameProcessor/Configuration/MqttOptions.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>Mqtt</c> section of <c>appsettings.json</c>. See SPEC.md §6.1.
+/// </summary>
+public sealed class MqttOptions
+{
+    public const string SectionName = "Mqtt";
+
+    [Required(AllowEmptyStrings = false)]
+    public string Host { get; set; } = string.Empty;
+
+    [Range(1, 65535)]
+    public int Port { get; set; } = 1883;
+
+    [Required(AllowEmptyStrings = false)]
+    public string ClientId { get; set; } = string.Empty;
+
+    public string? Username { get; set; }
+
+    public string? Password { get; set; }
+
+    public bool UseTls { get; set; }
+
+    [Required(AllowEmptyStrings = false)]
+    public string BaseTopic { get; set; } = "frames";
+
+    [Range(0, 2)]
+    public int PublishQos { get; set; } = 1;
+
+    [MinLength(1)]
+    public int[] RetryBackoffSeconds { get; set; } = Array.Empty<int>();
+}

src/FrameProcessor/Configuration/StorageOptions.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>Storage</c> section of <c>appsettings.json</c>. See SPEC.md §6.1, §7.
+/// </summary>
+public sealed class StorageOptions
+{
+    public const string SectionName = "Storage";
+
+    [Required(AllowEmptyStrings = false)]
+    public string ImageDirectory { get; set; } = string.Empty;
+}

src/FrameProcessor/Configuration/UrlFetchOptions.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>UrlFetch</c> section of <c>appsettings.json</c>. See SPEC.md §6.1, §8.
+/// </summary>
+public sealed class UrlFetchOptions
+{
+    public const string SectionName = "UrlFetch";
+
+    [Range(1, long.MaxValue)]
+    public long MaxBytes { get; set; } = 52_428_800L;
+
+    [Range(1, int.MaxValue)]
+    public int TimeoutSeconds { get; set; } = 30;
+
+    [Range(0, int.MaxValue)]
+    public int MaxRedirects { get; set; } = 3;
+}