feat: listening settings tab controls, warm-up button, resume button

- Listening tab: expose Speed, Auto-next, and Announce chapter controls
  alongside the existing Player Style row (chapters/[n]/+page.svelte)
- AudioPlayer: add Warm up Ch. N button in standard player ready state
  when autoNext is off; shows prefetching spinner and completion status
- Book page: fetch saved audioTime on mount; show Resume Ch. N button
  (desktop + mobile) that sets autoStartChapter and navigates directly

ui/src/lib/components/AudioPlayer.svelte

@@ -1345,6 +1345,47 @@
 					</span>
 				</div>
 			</div>
+
+			<!-- Warm-up next chapter (only when autoNext is off and next exists) -->
+			{#if !audioStore.autoNext && nextChapter != null}
+				<div class="mt-2 flex items-center gap-2">
+					{#if audioStore.nextStatus === 'none'}
+						<button
+							type="button"
+							onclick={prefetchNext}
+							class="flex items-center gap-1.5 text-xs text-(--color-muted) hover:text-(--color-brand) transition-colors"
+							title="Pre-generate audio for the next chapter"
+						>
+							<svg class="w-3.5 h-3.5" fill="currentColor" viewBox="0 0 24 24">
+								<path d="M7 2l10 10L7 22z"/>
+							</svg>
+							Warm up Ch. {nextChapter}
+						</button>
+					{:else if audioStore.nextStatus === 'prefetching'}
+						<span class="flex items-center gap-1.5 text-xs text-(--color-muted)">
+							<svg class="w-3.5 h-3.5 animate-spin" fill="none" viewBox="0 0 24 24">
+								<circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
+								<path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z"></path>
+							</svg>
+							Warming up Ch. {nextChapter}…
+						</span>
+					{:else if audioStore.nextStatus === 'prefetched'}
+						<span class="flex items-center gap-1.5 text-xs text-(--color-brand)">
+							<svg class="w-3.5 h-3.5" fill="currentColor" viewBox="0 0 24 24">
+								<path d="M9 16.17L4.83 12l-1.42 1.41L9 19 21 7l-1.41-1.41z"/>
+							</svg>
+							Ch. {nextChapter} ready
+						</span>
+					{:else if audioStore.nextStatus === 'failed'}
+						<span class="flex items-center gap-1.5 text-xs text-red-400">
+							<svg class="w-3.5 h-3.5" fill="currentColor" viewBox="0 0 24 24">
+								<path d="M19 6.41L17.59 5 12 10.59 6.41 5 5 6.41 10.59 12 5 17.59 6.41 19 12 13.41 17.59 19 19 17.59 13.41 12z"/>
+							</svg>
+							Warm-up failed
+						</span>
+					{/if}
+				</div>
+			{/if}
 		{/if}
 
 	{:else if audioStore.active}