Summary

• Adds a pre-flight check in start_microphone_stream() to detect when no audio input devices exist before hitting coreaudio
• Introduces a new no_input_device error type (following the existing microphone_permission_denied pattern)
• Shows a clear, actionable toast: "No Microphone Found" with a description guiding the user to connect a mic
• Adds translations for all 17 supported locales

Fixes #1114

⚠️ I have not validated the i18n keys besides en-US and pt-BR - they were all AI-gen

Changes

Backend (Rust):

• recorder.rs — Added is_no_input_device_error() detection helper + 3 unit tests
• managers/audio.rs — Pre-flight device enumeration check before rec.open()
• actions.rs — New "no_input_device" error type classification
• audio/mod.rs, audio_toolkit/mod.rs — Re-exports

Frontend (React/TS):

• App.tsx — New else if branch for the no_input_device error type
• All 17 translation.json files — Added noInputDeviceTitle and noInputDevice i18n keys

Before / After

Before: Failed to start recording: Failed to open recorder: Failed to fetch preferred config: A backend-specific error has occurred: An unknown error unknown to the coreaudio-rs API occurred

After: No Microphone Found — No audio input device was detected. Please connect a microphone or headset and try again.

Test plan

• cargo test -- recorder::tests — all 7 tests pass (including 3 new ones)
• bun run lint — passes clean
• Manual test on a machine without a mic (e.g., Mac Studio with no external mic): trigger recording → verify the friendly toast appears