Add speech-to-text feature using Faster Whisper container

Adds a mic button to the terminal UI that captures speech, transcribes
it via a Faster Whisper sidecar container, and injects the text into
the terminal input. Includes settings panel for model selection
(tiny/small/medium), port config, and container lifecycle management.

- stt-container/: Dockerfile + FastAPI server for Whisper transcription
- Rust backend: STT container management, transcribe_audio IPC command
- Frontend: useSTT hook, SttButton, SttSettings, WAV encoder
- CI: Gitea Actions workflow for multi-arch STT image builds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src-tauri/src/docker/mod.rs

@@ -3,7 +3,10 @@ pub mod container;
 pub mod image;
 pub mod exec;
 pub mod network;
+pub mod stt;
 
+#[allow(unused_imports)]
+pub use stt::*;
 #[allow(unused_imports)]
 pub use client::*;
 #[allow(unused_imports)]