feat: stream/generate audio mode toggle

Add a user-selectable playback mode stored in user_settings:
- 'stream' (default): /api/audio-stream starts playing within seconds,
  saves to MinIO concurrently — low latency
- 'generate': queue runner task, poll until full audio is ready in
  MinIO, then play via presigned URL — legacy behaviour

UI toggles in two places:
- AudioPlayer idle pill: compact '· Stream / · Generate' inline next
  to voice name and estimated duration
- ListeningMode controls row: pill alongside Auto, Announce, Sleep;
  disabled and grayed out for CF AI voices (batch-only, no streaming)

startPlayback() now branches on audioStore.audioMode for non-CF AI
voices; generate mode uses the same runner task + progress bar flow
as CF AI but without the preview clip.

PocketBase: audio_mode text field added to user_settings on
pb.libnovel.cc (live) and in pb-init-v3.sh (create block +
add_field migration line).

ui/src/routes/+layout.server.ts

@@ -17,7 +17,7 @@ export const load: LayoutServerLoad = async ({ locals, url, cookies }) => {
 		redirect(302, `/login`);
 	}
 
-	let settings = { autoNext: false, voice: 'af_bella', speed: 1.0, theme: 'amber', locale: 'en', fontFamily: 'system', fontSize: 1.0, announceChapter: false };
+	let settings = { autoNext: false, voice: 'af_bella', speed: 1.0, theme: 'amber', locale: 'en', fontFamily: 'system', fontSize: 1.0, announceChapter: false, audioMode: 'stream' };
 	try {
 		const row = await getSettings(locals.sessionId, locals.user?.id);
 		if (row) {
@@ -29,7 +29,8 @@ export const load: LayoutServerLoad = async ({ locals, url, cookies }) => {
 				locale: row.locale ?? 'en',
 				fontFamily: row.font_family ?? 'system',
 				fontSize: row.font_size || 1.0,
-				announceChapter: row.announce_chapter ?? false
+				announceChapter: row.announce_chapter ?? false,
+				audioMode: row.audio_mode ?? 'stream'
 			};
 		}
 	} catch (e) {

ui/src/routes/+layout.svelte

@@ -157,6 +157,7 @@
 				audioStore.voice = data.settings.voice;
 				audioStore.speed = data.settings.speed;
 				audioStore.announceChapter = data.settings.announceChapter ?? false;
+				audioStore.audioMode = (data.settings.audioMode === 'generate' ? 'generate' : 'stream');
 			}
 			// Always sync theme + font (profile page calls invalidateAll after saving)
 			currentTheme = data.settings.theme ?? 'amber';
@@ -179,6 +180,7 @@
 		const fontFamily = currentFontFamily;
 		const fontSize = currentFontSize;
 		const announceChapter = audioStore.announceChapter;
+		const audioMode = audioStore.audioMode;
 
 		// Skip saving until settings have been applied from the server AND
 		// at least one user-driven change has occurred after that.
@@ -189,7 +191,7 @@
 			fetch('/api/settings', {
 				method: 'PUT',
 				headers: { 'Content-Type': 'application/json' },
-				body: JSON.stringify({ autoNext, voice, speed, theme, fontFamily, fontSize, announceChapter })
+				body: JSON.stringify({ autoNext, voice, speed, theme, fontFamily, fontSize, announceChapter, audioMode })
 			}).catch(() => {});
 		}, 800) as unknown as number;
 	});

ui/src/routes/api/settings/+server.ts

@@ -5,7 +5,7 @@ import { log } from '$lib/server/logger';
 
 /**
  * GET /api/settings
- * Returns the current user's settings (auto_next, voice, speed, theme, locale, fontFamily, fontSize, announceChapter).
+ * Returns the current user's settings (auto_next, voice, speed, theme, locale, fontFamily, fontSize, announceChapter, audioMode).
  * Returns defaults if no settings record exists yet.
  */
 export const GET: RequestHandler = async ({ locals }) => {
@@ -19,7 +19,8 @@ export const GET: RequestHandler = async ({ locals }) => {
 			locale: settings?.locale ?? 'en',
 			fontFamily: settings?.font_family ?? 'system',
 			fontSize: settings?.font_size || 1.0,
-			announceChapter: settings?.announce_chapter ?? false
+			announceChapter: settings?.announce_chapter ?? false,
+			audioMode: settings?.audio_mode ?? 'stream'
 		});
 	} catch (e) {
 		log.error('settings', 'GET failed', { err: String(e) });
@@ -29,7 +30,7 @@ export const GET: RequestHandler = async ({ locals }) => {
 
 /**
  * PUT /api/settings
- * Body: { autoNext: boolean, voice: string, speed: number, theme?: string, locale?: string, fontFamily?: string, fontSize?: number, announceChapter?: boolean }
+ * Body: { autoNext: boolean, voice: string, speed: number, theme?: string, locale?: string, fontFamily?: string, fontSize?: number, announceChapter?: boolean, audioMode?: string }
  * Saves user preferences.
  */
 export const PUT: RequestHandler = async ({ request, locals }) => {
@@ -73,6 +74,12 @@ export const PUT: RequestHandler = async ({ request, locals }) => {
 		error(400, 'Invalid announceChapter — must be boolean');
 	}
 
+	// audioMode is optional — if provided it must be a known value
+	const validAudioModes = ['stream', 'generate'];
+	if (body.audioMode !== undefined && !validAudioModes.includes(body.audioMode)) {
+		error(400, `Invalid audioMode — must be one of: ${validAudioModes.join(', ')}`);
+	}
+
 	try {
 		await saveSettings(locals.sessionId, body, locals.user?.id);
 	} catch (e) {