fix(ios): add Swift 6 strict concurrency compatibility

Applies the same Swift 6 compatibility patterns from PR #166 (macOS) to the iOS app.

Changes:
- LocationService.swift: Added Sendable constraint to withTimeout<T> generic,
  made CLLocationManagerDelegate methods nonisolated with Task { @MainActor in }
  pattern to safely access MainActor state
- TalkModeManager.swift: Fixed OSLog string interpolation to avoid operator
  overload issues with OSLogMessage in Swift 6

Addresses #164

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ios/Sources/Voice/TalkModeManager.swift

@@ -288,9 +288,8 @@ final class TalkModeManager: NSObject {
             self.chatSubscribedSessionKeys.insert(key)
             self.logger.info("chat.subscribe ok sessionKey=\(key, privacy: .public)")
         } catch {
-            self.logger.warning(
-                "chat.subscribe failed sessionKey=\(key, privacy: .public) " +
-                    "err=\(error.localizedDescription, privacy: .public)")
+            let err = error.localizedDescription
+            self.logger.warning("chat.subscribe failed key=\(key, privacy: .public) err=\(err, privacy: .public)")
         }
     }
 
@@ -528,9 +527,8 @@ final class TalkModeManager: NSObject {
                     self.lastPlaybackWasPCM = false
                     result = await self.mp3Player.play(stream: stream)
                 }
-                self.logger.info(
-                    "elevenlabs stream finished=\(result.finished, privacy: .public) " +
-                        "dur=\(Date().timeIntervalSince(started), privacy: .public)s")
+                let duration = Date().timeIntervalSince(started)
+                self.logger.info("elevenlabs stream finished=\(result.finished, privacy: .public) dur=\(duration, privacy: .public)s")
                 if !result.finished, let interruptedAt = result.interruptedAt {
                     self.lastInterruptedAtSeconds = interruptedAt
                 }