feat(ios): rework audio presets — always-available + device-specific

Presets reorganized to give users choice at every level:

Always available (work with any output route):
- Voice Chat: AEC/AGC/HPF on, mono, system picks best route (BT HFP,
  wired, or speaker). The standard iOS VoIP experience.
- Stereo Mic: Stereo built-in mic (front+back capsules), A2DP output
  if BT connected else speaker/wired. Standard processing.
- Studio (No Processing): Stereo mic, no AEC/AGC/HPF (raw mode).
  Maximum fidelity. Echo risk on speaker.

When Bluetooth connected:
- Bluetooth Headset (HFP): BT mic + BT output, AEC on, mono.
- BT Headphones + Mono Mic: A2DP output + built-in mic, mono, no AEC.
- BT Headphones + Stereo Mic: A2DP output + stereo built-in mic.

When wired headset/earpods connected:
- Wired Headset: Wired output + wired/built-in mic, AEC on, mono.

Always:
- Custom: shown when advanced settings don't match any preset.

Key changes from previous version:
- Stereo Mic is no longer gated behind Bluetooth — it's always available
  and uses A2DP output if BT is connected, else speaker/wired.
- Wired headset detection (headphones/headsetMic/usbAudio port types)
  with a dedicated preset.
- Voice Chat preset always available with AEC — the safe default.
- activePreset checks device-specific presets first so e.g. when BT is
  connected and settings match 'Bluetooth Headset', it returns that
  instead of the equivalent 'Voice Chat'.
- detectAudioDevices() replaces detectBluetooth(), detects both BT and
  wired devices from currentRoute + availableInputs.

clients/apple/iOS/VoiceCatiOS/Views/SettingsView.swift

@@ -23,11 +23,11 @@ struct SettingsView: View {
                     }
                     .accessibilityLabel("Audio preset")
 
-                    if !router.hasBluetoothDevice {
-                        Text("Connect Bluetooth headphones to see Bluetooth presets.")
+                    if !router.hasBluetoothDevice && !router.hasWiredHeadset {
+                        Text("Connect Bluetooth headphones or a wired headset for more presets.")
                             .font(.caption)
                             .foregroundStyle(.secondary)
-                            .accessibilityLabel("No Bluetooth device connected")
+                            .accessibilityLabel("No external audio device connected")
                     }
                 }