iOS: stem playlist refresh and covers, download queue page, reorderable Library, whole-library radio

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Stemify/Cache/MediaCache.swift

@@ -498,7 +498,7 @@ final class CachedResource: @unchecked Sendable {
                 block = 0
                 lastBlock = MediaCache.blocksFor(Int64(body.count)) - 1
             default:
-                throw MediaError("HTTP \(resp.statusCode) fetching media")
+                throw MediaError("HTTP \(resp.statusCode) fetching media from \(u.host ?? "?")\(u.port.map { ":\($0)" } ?? "")\(u.path)")
             }
             cond.lock()
             let length = self.length