fix(ios): rename allowBluetooth -> allowBluetoothHFP (iOS 26 SDK)

Xcode warning on iOS SDK 26+:
  'allowBluetooth' was deprecated in iOS 8.0: renamed to
  'AVAudioSession.CategoryOptions.allowBluetoothHFP'

The flag was renamed in iOS 8 (a decade ago) but the old name has
been kept as a soft-deprecated alias. iOS 26 SDK finally emits the
warning, and -Werror builds would fail on it. Same semantics:
permit HFP-profile Bluetooth headsets as input + output. Kept
.allowBluetoothA2DP alongside for higher-quality output-only A2DP
devices.

flutter build ios --release --no-codesign: 10.7 s, Runner.app
30.0 MB.

apps/chanora_flutter/ios/Runner/AppDelegate.swift

@@ -32,7 +32,13 @@ import AVFoundation
       try session.setCategory(
         .playAndRecord,
         mode: .voiceChat,
-        options: [.defaultToSpeaker, .allowBluetooth, .allowBluetoothA2DP]
+        // .allowBluetoothHFP is the iOS-26-renamed form of the
+        // historical .allowBluetooth flag — same semantics (permit
+        // HFP-profile Bluetooth headsets as input + output, so
+        // AirPods et al. route both directions). .allowBluetoothA2DP
+        // covers higher-quality output-only A2DP devices that lack
+        // a mic. Keeping both gives us the broadest BT support.
+        options: [.defaultToSpeaker, .allowBluetoothHFP, .allowBluetoothA2DP]
       )
       NSLog("chanora_flutter: AVAudioSession category set (playAndRecord/voiceChat)")
     } catch {