feat: add ShazamService for music recognition

Music/Services/ShazamService.swift

@@ -0,0 +1,83 @@
+import AVFAudio
+import Observation
+import ShazamKit
+
+@Observable
+final class ShazamService: NSObject, SHSessionDelegate {
+    var isListening = false
+    var matchedTitle: String?
+    var matchedArtist: String?
+    var errorMessage: String?
+
+    private var session: SHSession?
+    private let audioEngine = AVAudioEngine()
+    private var timeoutTask: Task<Void, Never>?
+
+    func startListening() {
+        guard !isListening else {
+            stopListening()
+            return
+        }
+
+        matchedTitle = nil
+        matchedArtist = nil
+        errorMessage = nil
+
+        let session = SHSession()
+        session.delegate = self
+        self.session = session
+
+        let inputNode = audioEngine.inputNode
+        let format = inputNode.outputFormat(forBus: 0)
+
+        inputNode.installTap(onBus: 0, bufferSize: 2048, format: format) { buffer, time in
+            session.matchStreamingBuffer(buffer, at: time)
+        }
+
+        do {
+            try audioEngine.start()
+            isListening = true
+
+            timeoutTask = Task { [weak self] in
+                try? await Task.sleep(for: .seconds(15))
+                guard !Task.isCancelled else { return }
+                self?.stopListening()
+                if self?.matchedTitle == nil {
+                    self?.errorMessage = "No match found. Try again in a quieter environment."
+                }
+            }
+        } catch {
+            errorMessage = "Could not access microphone."
+        }
+    }
+
+    func stopListening() {
+        timeoutTask?.cancel()
+        timeoutTask = nil
+        if audioEngine.isRunning {
+            audioEngine.inputNode.removeTap(onBus: 0)
+            audioEngine.stop()
+        }
+        session = nil
+        isListening = false
+    }
+
+    func clearResult() {
+        matchedTitle = nil
+        matchedArtist = nil
+        errorMessage = nil
+    }
+
+    nonisolated func session(_ session: SHSession, didFind match: SHMatch) {
+        Task { @MainActor [weak self] in
+            guard let item = match.mediaItems.first else { return }
+            self?.matchedTitle = item.title
+            self?.matchedArtist = item.artist
+            self?.stopListening()
+        }
+    }
+
+    nonisolated func session(_ session: SHSession, didNotFindMatchFor signature: SHSignature) {
+        // Session continues listening; the 15s timeout handles the "no match" case.
+    }
+}