feat: profile stats, discover history, end-of-chapter sleep, rating-ranked deck

**Profile stats tab**
- New Stats tab on /profile page (Profile / Stats switcher)
- Reading overview: chapters read, completed, reading, plan-to-read counts
- Activity cards: day streak + avg rating given
- Favourite genres (top 3 by frequency across library/progress)
- getUserStats() in pocketbase.ts — computes streak, shelf counts, genre freq

**Discover history tab**
- New History tab on /discover with full voted-book list
- Per-entry: cover thumbnail, title link, author, action label (Liked/Skipped/etc.)
- Undo button: optimistic update + DELETE /api/discover/vote?slug=...
- Clear all history button; tab shows vote count badge
- getVotedBooks(), undoDiscoveryVote() in pocketbase.ts

**Rating-ranked discovery deck**
- getBooksForDiscovery now sorts by community avg rating before returning
- Tier-based shuffle: books within the same ±0.5 star bucket are still randomised
- Higher-rated books surface earlier without making the deck fully deterministic

**End-of-chapter sleep timer**
- New cycle option: Off → End of Chapter → 15m → 30m → 45m → 60m → Off
- sleepAfterChapter flag in AudioStore; layout handles it in onended (skips auto-next)
- Button shows "End Ch." label when active in this mode

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/lib/components/AudioPlayer.svelte

@@ -699,16 +699,22 @@
 	});
 
 	function cycleSleepTimer() {
-		if (!audioStore.sleepUntil) {
-			// Start at first option (15 min)
+		// Currently: no timer active at all
+		if (!audioStore.sleepUntil && !audioStore.sleepAfterChapter) {
+			audioStore.sleepAfterChapter = true;
+			return;
+		}
+		// Currently: end-of-chapter mode — move to 15m
+		if (audioStore.sleepAfterChapter) {
+			audioStore.sleepAfterChapter = false;
 			audioStore.sleepUntil = Date.now() + SLEEP_OPTIONS[0] * 60 * 1000;
 			return;
 		}
+		// Currently: timed mode — cycle to next or turn off
 		const remaining = audioStore.sleepUntil - Date.now();
 		const currentMin = Math.round(remaining / 60000);
-		const idx = SLEEP_OPTIONS.findIndex(m => m >= currentMin);
+		const idx = SLEEP_OPTIONS.findIndex((m) => m >= currentMin);
 		if (idx === -1 || idx === SLEEP_OPTIONS.length - 1) {
-			// Was at max or past last — turn off
 			audioStore.sleepUntil = 0;
 		} else {
 			audioStore.sleepUntil = Date.now() + SLEEP_OPTIONS[idx + 1] * 60 * 1000;
@@ -933,14 +939,20 @@
 				<Button
 					variant="ghost"
 					size="sm"
-					class={cn('gap-1 text-xs flex-shrink-0', audioStore.sleepUntil ? 'text-(--color-brand) bg-(--color-brand)/15 hover:bg-(--color-brand)/25' : 'text-(--color-muted)')}
+					class={cn('gap-1 text-xs flex-shrink-0', audioStore.sleepUntil || audioStore.sleepAfterChapter ? 'text-(--color-brand) bg-(--color-brand)/15 hover:bg-(--color-brand)/25' : 'text-(--color-muted)')}
 					onclick={cycleSleepTimer}
-					title={audioStore.sleepUntil ? `Sleep timer: ${formatSleepRemaining(sleepRemainingSec)} remaining` : 'Sleep timer off'}
+					title={audioStore.sleepAfterChapter
+						? 'Stop after this chapter'
+						: audioStore.sleepUntil
+							? `Sleep timer: ${formatSleepRemaining(sleepRemainingSec)} remaining`
+							: 'Sleep timer off'}
 				>
 					<svg class="w-3.5 h-3.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
 						<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z"/>
 					</svg>
-					{#if audioStore.sleepUntil}
+					{#if audioStore.sleepAfterChapter}
+						End Ch.
+					{:else if audioStore.sleepUntil}
 						{formatSleepRemaining(sleepRemainingSec)}
 					{:else}
 						Sleep