Add voice notes: on-device transcription, multi-language, watch capture

- Schema v2: Note.AudioInfo, .m4a sidecar next to the note JSON in iCloud
- AudioRecorderService (iOS/macOS) + SpeechAnalyzer transcription pipeline
  with enabled-language set and confidence-based auto-pick, re-transcribe menu
- Settings > Transcription > Languages with asset download/reserve handling
- watchOS app + accessory complication: one-button recorder, WCSession
  transferFile to phone, WatchInbox staging, direct-upsert ingestion
- Player UI, transcription status chips, quick-capture mic in notes list
- Version 0.2, changelog + README updated

Shared/Connectivity/AudioNotePayload.swift

@@ -0,0 +1,73 @@
+import Foundation
+
+/// Versioned metadata carried alongside a watch audio recording over
+/// `WCSession.transferFile(_:metadata:)`. The watch encodes it into the
+/// transfer's metadata dictionary; the phone decodes it on delivery.
+///
+/// Versioned so a newer watch build can extend the field set without an older
+/// phone build silently misreading it: a missing, unknown, or newer version
+/// decodes to `nil` (a forward gate). On that outcome the phone still stages the
+/// audio bytes but skips ingest, so a future phone build can pick them up.
+///
+/// Lives in `Shared/`, compiled into the iOS app and the watch app (not the Mac
+/// app). Foundation-only, so it is safe on both platforms.
+struct AudioNotePayload: Equatable, Sendable {
+    /// The wire version this build writes. Bump only when the field set changes
+    /// in a way an older decoder can't interpret.
+    static let currentVersion = 1
+
+    /// ULID string minted on the watch at record start — the note's identity and
+    /// its UTC time bucket. Also the staged filename base on the phone.
+    let id: String
+    /// Wall-clock instant recording started.
+    let recordedAt: Date
+    /// Recording length in seconds.
+    let duration: TimeInterval
+    /// IANA time-zone identifier the recording was made in (e.g. "Europe/Berlin"),
+    /// or nil if unknown.
+    let timeZoneID: String?
+
+    private enum Key {
+        static let version = "v"
+        static let id = "id"
+        static let recordedAt = "recordedAt"
+        static let duration = "duration"
+        static let timeZone = "tz"
+    }
+
+    init(id: String, recordedAt: Date, duration: TimeInterval, timeZoneID: String?) {
+        self.id = id
+        self.recordedAt = recordedAt
+        self.duration = duration
+        self.timeZoneID = timeZoneID
+    }
+
+    /// A plist-serializable dictionary for `WCSession.transferFile(_:metadata:)`.
+    /// Every value type (Int, String, Date, Double) survives WatchConnectivity's
+    /// metadata plist encoding.
+    func metadata() -> [String: Any] {
+        var dict: [String: Any] = [
+            Key.version: Self.currentVersion,
+            Key.id: id,
+            Key.recordedAt: recordedAt,
+            Key.duration: duration,
+        ]
+        if let timeZoneID { dict[Key.timeZone] = timeZoneID }
+        return dict
+    }
+
+    /// Decode a received metadata dictionary. Returns `nil` when the version is
+    /// missing, unknown, or newer than this build understands (the forward gate),
+    /// or when a required field is absent or malformed.
+    init?(metadata: [String: Any]) {
+        guard let version = metadata[Key.version] as? Int,
+              version >= 1, version <= Self.currentVersion,
+              let id = metadata[Key.id] as? String,
+              let recordedAt = metadata[Key.recordedAt] as? Date,
+              let duration = metadata[Key.duration] as? Double else { return nil }
+        self.id = id
+        self.recordedAt = recordedAt
+        self.duration = duration
+        self.timeZoneID = metadata[Key.timeZone] as? String
+    }
+}