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/components/terminal/TerminalView.tsx

@@ -7,6 +7,7 @@ import { openUrl } from "@tauri-apps/plugin-opener";
 import "@xterm/xterm/css/xterm.css";
 import { useTerminal } from "../../hooks/useTerminal";
 import { useAppState } from "../../store/appState";
+import SttButton from "./SttButton";
 import { awsSsoRefresh } from "../../lib/tauri-commands";
 import { UrlDetector } from "../../lib/urlDetector";
 import UrlToast from "./UrlToast";
@@ -25,6 +26,7 @@ export default function TerminalView({ sessionId, active }: Props) {
   const detectorRef = useRef<UrlDetector | null>(null);
   const { sendInput, pasteImage, resize, onOutput, onExit } = useTerminal();
   const setTerminalHasSelection = useAppState(s => s.setTerminalHasSelection);
+  const sttEnabled = useAppState(s => s.appSettings?.stt?.enabled);
 
   const ssoBufferRef = useRef("");
   const ssoTriggeredRef = useRef(false);
@@ -424,6 +426,8 @@ export default function TerminalView({ sessionId, active }: Props) {
       >
         {isAutoFollow ? "▼ Following" : "▽ Paused"}
       </button>
+      {/* STT mic button - bottom left */}
+      {sttEnabled && <SttButton sessionId={sessionId} sendInput={sendInput} />}
       {/* Jump to Current - bottom right, when scrolled up */}
       {!isAtBottom && (
         <button