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/commands/stt_commands.rs

@@ -0,0 +1,92 @@
+use tauri::{AppHandle, Emitter, State};
+
+use crate::docker::stt;
+use crate::models::app_settings::SttStatus;
+use crate::AppState;
+
+#[tauri::command]
+pub async fn get_stt_status(state: State<'_, AppState>) -> Result<SttStatus, String> {
+    let settings = state.settings_store.get();
+    stt::get_stt_status(&settings.stt).await
+}
+
+#[tauri::command]
+pub async fn start_stt(state: State<'_, AppState>) -> Result<SttStatus, String> {
+    let settings = state.settings_store.get();
+    stt::ensure_stt_running(&settings.stt).await
+}
+
+#[tauri::command]
+pub async fn stop_stt() -> Result<(), String> {
+    stt::stop_stt_container().await
+}
+
+#[tauri::command]
+pub async fn build_stt_image(app_handle: AppHandle) -> Result<(), String> {
+    stt::build_stt_image(move |msg| {
+        let _ = app_handle.emit("stt-build-progress", &msg);
+    })
+    .await
+}
+
+#[tauri::command]
+pub async fn pull_stt_image(app_handle: AppHandle) -> Result<(), String> {
+    stt::pull_stt_image(move |msg| {
+        let _ = app_handle.emit("stt-pull-progress", &msg);
+    })
+    .await
+}
+
+#[tauri::command]
+pub async fn transcribe_audio(
+    audio_data: Vec<u8>,
+    state: State<'_, AppState>,
+) -> Result<String, String> {
+    let settings = state.settings_store.get();
+    if !settings.stt.enabled {
+        return Err("STT is not enabled".to_string());
+    }
+
+    let url = format!("http://127.0.0.1:{}/transcribe", settings.stt.port);
+
+    let file_part = reqwest::multipart::Part::bytes(audio_data)
+        .file_name("recording.wav")
+        .mime_str("audio/wav")
+        .map_err(|e| format!("Failed to create multipart: {}", e))?;
+
+    let mut form = reqwest::multipart::Form::new().part("file", file_part);
+
+    if let Some(ref lang) = settings.stt.language {
+        form = form.text("language", lang.clone());
+    }
+
+    let client = reqwest::Client::new();
+    let response = client
+        .post(&url)
+        .multipart(form)
+        .send()
+        .await
+        .map_err(|e| {
+            if e.is_connect() {
+                "STT container is not running. Start it from Settings.".to_string()
+            } else {
+                format!("Transcription request failed: {}", e)
+            }
+        })?;
+
+    if !response.status().is_success() {
+        let status = response.status();
+        let body = response.text().await.unwrap_or_default();
+        return Err(format!("Transcription failed ({}): {}", status, body));
+    }
+
+    let result: serde_json::Value = response
+        .json()
+        .await
+        .map_err(|e| format!("Failed to parse transcription response: {}", e))?;
+
+    result["text"]
+        .as_str()
+        .map(|s| s.to_string())
+        .ok_or_else(|| "No text in transcription response".to_string())
+}