Clean up dead code, consolidate duplication, fix redundancies

Remove 9 dead methods, 6 unused constants, and redundant
ReaderWriterLockSlim from MetadataCache. Consolidate repeated
patterns into HasChapters, IsPlayable, and ToLowerString helpers.
Extract shared API methods in SRFApiClient. Move variant manifest
rewriting from controller to StreamProxyService. Make Auto quality
distinct from HD. Update README architecture section.

Jellyfin.Plugin.SRFPlay/Controllers/StreamProxyController.cs

@@ -196,7 +196,23 @@ public class StreamProxyController : ControllerBase
             var manifestContent = System.Text.Encoding.UTF8.GetString(manifestData);
             var scheme = GetProxyScheme();
             var baseProxyUrl = $"{scheme}://{Request.Host}/Plugins/SRFPlay/Proxy/{itemId}";
-            var rewrittenContent = RewriteSegmentUrls(manifestContent, baseProxyUrl);
+
+            // Extract query parameters from the current request to propagate them
+            string queryParams;
+            if (Request.Query.TryGetValue("token", out var tokenVal) && !string.IsNullOrEmpty(tokenVal))
+            {
+                queryParams = $"?token={tokenVal}";
+            }
+            else if (Request.Query.TryGetValue("itemId", out var itemIdVal) && !string.IsNullOrEmpty(itemIdVal))
+            {
+                queryParams = $"?itemId={itemIdVal}";
+            }
+            else
+            {
+                queryParams = string.Empty;
+            }
+
+            var rewrittenContent = _proxyService.RewriteVariantManifestUrls(manifestContent, baseProxyUrl, queryParams);
 
             // Set cache headers based on stream type (live vs VOD)
             AddManifestCacheHeaders(actualItemId);
@@ -311,81 +327,6 @@ public class StreamProxyController : ControllerBase
         return pathItemId;
     }
 
-    /// <summary>
-    /// Rewrites segment URLs in a manifest to point to proxy.
-    /// </summary>
-    /// <param name="manifestContent">The manifest content.</param>
-    /// <param name="baseProxyUrl">The base proxy URL.</param>
-    /// <returns>The rewritten manifest.</returns>
-    private string RewriteSegmentUrls(string manifestContent, string baseProxyUrl)
-    {
-        // Extract query parameters from the current request to propagate them
-        string queryParams;
-        if (Request.Query.TryGetValue("token", out var token) && !string.IsNullOrEmpty(token))
-        {
-            queryParams = $"?token={token}";
-        }
-        else if (Request.Query.TryGetValue("itemId", out var itemId) && !string.IsNullOrEmpty(itemId))
-        {
-            queryParams = $"?itemId={itemId}";
-        }
-        else
-        {
-            queryParams = string.Empty;
-        }
-
-        // Helper function to rewrite a single URL
-        string RewriteUrl(string url)
-        {
-            if (url.Contains("://", StringComparison.Ordinal))
-            {
-                // Absolute URL - extract filename and rewrite
-                var uri = new Uri(url.Trim());
-                var segments = uri.AbsolutePath.Split('/');
-                var fileName = segments[^1];
-                return $"{baseProxyUrl}/{fileName}{queryParams}";
-            }
-
-            // Relative URL - rewrite to proxy
-            return $"{baseProxyUrl}/{url.Trim()}{queryParams}";
-        }
-
-        var lines = manifestContent.Split('\n');
-        var result = new System.Text.StringBuilder();
-
-        foreach (var line in lines)
-        {
-            if (string.IsNullOrWhiteSpace(line))
-            {
-                result.AppendLine(line);
-            }
-            else if (line.StartsWith('#'))
-            {
-                // HLS tag line - check for URI="..." attributes (e.g., #EXT-X-MAP:URI="init.mp4")
-                if (line.Contains("URI=\"", StringComparison.Ordinal))
-                {
-                    var rewrittenLine = System.Text.RegularExpressions.Regex.Replace(
-                        line,
-                        @"URI=""([^""]+)""",
-                        match => $"URI=\"{RewriteUrl(match.Groups[1].Value)}\"");
-                    result.AppendLine(rewrittenLine);
-                }
-                else
-                {
-                    // Keep other metadata lines as-is
-                    result.AppendLine(line);
-                }
-            }
-            else
-            {
-                // Non-tag line with URL - rewrite it
-                result.AppendLine(RewriteUrl(line));
-            }
-        }
-
-        return result.ToString();
-    }
-
     /// <summary>
     /// Proxies image requests from SRF CDN, fixing Content-Type headers.
     /// </summary>