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>

doc/research/reference-sources/chaosflix/Jellyfin.Plugin.Chaosflix/Api/ProxyUrl.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Jellyfin.Plugin.Chaosflix.Api;
+
+/// <summary>
+/// Reads back a proxy url the channel handed out, so a diagnostic can check it and show
+/// it without handing the reader a url they could stream through.
+/// </summary>
+internal static class ProxyUrl
+{
+    private const string FolderParameter = "recordingFolder";
+    private const string LanguageParameter = "language";
+
+    /// <summary>
+    /// Renders the url without its signature. The result is rebuilt from the parts that
+    /// were understood rather than edited in place, so nothing of the signature can
+    /// survive a url shaped differently than expected.
+    /// </summary>
+    internal static string Redact(string url)
+    {
+        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
+        {
+            return "<unparseable proxy url>";
+        }
+
+        var query = Parse(uri);
+        var parts = new List<string>();
+        if (query.TryGetValue(FolderParameter, out var folder))
+        {
+            parts.Add($"{FolderParameter}={folder}");
+        }
+
+        if (query.TryGetValue(LanguageParameter, out var language))
+        {
+            parts.Add($"{LanguageParameter}={language}");
+        }
+
+        parts.Add($"{ProxySignature.QueryParameter}=<redacted>");
+        return $"{uri.GetLeftPart(UriPartial.Path)}?{string.Join('&', parts)}";
+    }
+
+    /// <summary>
+    /// Whether the url carries a signature the proxy endpoint would accept for exactly
+    /// the recording the url names.
+    /// </summary>
+    internal static bool IsSignedCorrectly(string url)
+    {
+        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
+        {
+            return false;
+        }
+
+        var guid = uri.Segments.LastOrDefault()?.TrimEnd('/');
+        if (string.IsNullOrEmpty(guid))
+        {
+            return false;
+        }
+
+        var query = Parse(uri);
+        query.TryGetValue(ProxySignature.QueryParameter, out var signature);
+        return ProxySignature.Verify(
+            Uri.UnescapeDataString(guid),
+            query.GetValueOrDefault(FolderParameter),
+            query.GetValueOrDefault(LanguageParameter),
+            signature);
+    }
+
+    private static Dictionary<string, string> Parse(Uri uri)
+    {
+        var query = new Dictionary<string, string>(StringComparer.Ordinal);
+        foreach (var pair in uri.Query.TrimStart('?').Split('&', StringSplitOptions.RemoveEmptyEntries))
+        {
+            var separator = pair.IndexOf('=', StringComparison.Ordinal);
+            if (separator > 0)
+            {
+                query[pair[..separator]] = Uri.UnescapeDataString(pair[(separator + 1)..]);
+            }
+        }
+
+        return query;
+    }
+}