Floatplane channel plugin for Jellyfin 10.10.x: browse, HLS proxy, cookie session, CI release

- IChannel: creators -> sub-channels -> video posts (public listing API, search mapped)
- IRequiresMediaInfoCallback -> signed proxy URLs; stream controller rewrites HLS so the
  AES-128 key is fetched server-side with the session cookie, segments stay on the CDN
- delivery/info cached per token lifetime and throttled (~2/min)
- config page: paste sails.sid + validate, extra creators, quality, search test
- scripts/package.sh -> plugin folder + zip + md5 + manifest.json; Gitea release workflow
- research docs, HAR analysis (HAR itself gitignored), install-pi5.sh

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Jellyfin.Plugin.Floatplane/Api/Models/Common.cs

@@ -0,0 +1,127 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Jellyfin.Plugin.Floatplane.Api.Models;
+
+/// <summary>Image with optional pre-scaled variants (<c>pbs.floatplane.com</c>, public).</summary>
+public class ImageModel
+{
+    public int Width { get; set; }
+
+    public int Height { get; set; }
+
+    public string Path { get; set; } = string.Empty;
+
+    public List<ImageModel> ChildImages { get; set; } = new();
+
+    /// <summary>Largest variant whose width does not exceed <paramref name="maxWidth"/>, else the original.</summary>
+    public string BestPath(int maxWidth = 1200)
+    {
+        var candidates = ChildImages.Where(c => c.Width <= maxWidth && !string.IsNullOrEmpty(c.Path)).OrderByDescending(c => c.Width).ToList();
+        if (candidates.Count > 0)
+        {
+            return candidates[0].Path;
+        }
+
+        return Path;
+    }
+}
+
+/// <summary>Error envelope Floatplane returns for 4xx responses.</summary>
+public class ApiErrorModel
+{
+    public string? Id { get; set; }
+
+    public List<ApiErrorItem> Errors { get; set; } = new();
+
+    public string? Message { get; set; }
+
+    public bool Has(string name) => Errors.Any(e => string.Equals(e.Name, name, StringComparison.OrdinalIgnoreCase));
+}
+
+public class ApiErrorItem
+{
+    public string? Id { get; set; }
+
+    public string? Name { get; set; }
+
+    public string? Message { get; set; }
+}
+
+/// <summary>
+/// Floatplane sometimes sends a related object inline and sometimes only its id
+/// (e.g. <c>channel</c> on a post, <c>videoAttachments</c> in list responses).
+/// This converter accepts both: a string becomes <c>{ Id = string }</c>.
+/// </summary>
+/// <typeparam name="T">Model type with an <c>Id</c> property.</typeparam>
+public class IdOrObjectConverter<T> : JsonConverter<T>
+    where T : class, IHasId, new()
+{
+    public override T? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        if (reader.TokenType == JsonTokenType.Null)
+        {
+            return null;
+        }
+
+        if (reader.TokenType == JsonTokenType.String)
+        {
+            return new T { Id = reader.GetString() ?? string.Empty, IsReferenceOnly = true };
+        }
+
+        // Avoid infinite recursion: deserialise with a copy of the options minus this converter.
+        var inner = new JsonSerializerOptions(options);
+        var self = inner.Converters.FirstOrDefault(c => c is IdOrObjectConverter<T>);
+        if (self != null)
+        {
+            inner.Converters.Remove(self);
+        }
+
+        return JsonSerializer.Deserialize<T>(ref reader, inner);
+    }
+
+    public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+    {
+        var inner = new JsonSerializerOptions(options);
+        var self = inner.Converters.FirstOrDefault(c => c is IdOrObjectConverter<T>);
+        if (self != null)
+        {
+            inner.Converters.Remove(self);
+        }
+
+        JsonSerializer.Serialize(writer, value, inner);
+    }
+}
+
+public interface IHasId
+{
+    string Id { get; set; }
+
+    /// <summary>True when only the id was present in the JSON.</summary>
+    bool IsReferenceOnly { get; set; }
+}
+
+/// <summary>Shared serializer options for Floatplane JSON.</summary>
+public static class FloatplaneJson
+{
+    public static JsonSerializerOptions Options { get; } = Create();
+
+    private static JsonSerializerOptions Create()
+    {
+        var o = new JsonSerializerOptions
+        {
+            PropertyNameCaseInsensitive = true,
+            NumberHandling = JsonNumberHandling.AllowReadingFromString,
+            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        };
+        o.Converters.Add(new IdOrObjectConverter<ChannelModel>());
+        o.Converters.Add(new IdOrObjectConverter<CreatorModel>());
+        o.Converters.Add(new IdOrObjectConverter<VideoModel>());
+        o.Converters.Add(new JsonStringEnumConverter());
+        return o;
+    }
+}