Add Hi-Res authenticity check

Introduce a per-file Hi-Res authenticity checker and optional auto re-download for flagged fake Hi-Res downloads. Adds Rust checker modules (fft, evidence, FLAC/WAV decoding, tests) and a mobile API (check_hires_authenticity). Wire platform bindings for Android/iOS and PlatformBridge. Add Dart HiResCheckService, UI HiResCheckCard, settings toggle (redownloadFakeHiRes) and integration in the download pipeline to quarantine and replace suspicious files with LOSSLESS when safe. Adds claxon FLAC dependency.

ios/Runner/AppDelegate.swift

@@ -464,6 +464,11 @@ import UniformTypeIdentifiers
             let filePath = args["file_path"] as! String
             return try coreBackend.readFileMetadata(path: filePath, hint: args["display_name"] as? String ?? "")
 
+        case "checkHiResAuthenticity":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            return try coreBackend.checkHiResAuthenticity(path: filePath, optionsJson: args["options_json"] as? String ?? "")
+
         case "editFileMetadata":
             let args = call.arguments as! [String: Any]
             let filePath = args["file_path"] as! String

ios/Runner/CoreBackend.swift

@@ -164,6 +164,7 @@ protocol CoreBackend {
     func sanitizeFilename(filename: String) -> String
     func fileMetadataImplementation(path: String) -> String
     func readFileMetadata(path: String, hint: String) throws -> String
+    func checkHiResAuthenticity(path: String, optionsJson: String) throws -> String
     func editFileMetadata(path: String, metadataJson: String) throws -> String
     func reEnrichFile(requestJson: String) throws -> String
     func rewriteSplitArtistTags(path: String, artist: String, albumArtist: String) throws -> String
@@ -483,6 +484,10 @@ final class RustCoreBackend: CoreBackend {
         try SpotiFLACBackend.readFileMetadata(path: path, hint: hint, lease: nil)
     }
 
+    func checkHiResAuthenticity(path: String, optionsJson: String) throws -> String {
+        try SpotiFLACBackend.checkHiresAuthenticity(path: path, optionsJson: optionsJson, lease: nil)
+    }
+
     func editFileMetadata(path: String, metadataJson: String) throws -> String {
         try owner().editFileMetadata(path: URL(fileURLWithPath: path).resolvingSymlinksInPath().standardizedFileURL.path, metadataJson: metadataJson, lease: nil)
     }