feat(audio-player): end-time label toggles total / book-left / chapter-left (plan §10 web)

Clicking the end time cycles the three display modes, persisted per
device in localStorage (audio_time_display). Pure helpers (mode list,
normalize, cycle, endTimeLabel with 0-clamp and no-chapters fallback
to book remaining) + vitest; aria-label announces the current mode and
the next. Remaining values track the scrub cursor mid-drag. 140 unit
tests; 15 Playwright checks on KJV + Gardens.

templates/audio_reader.templ

@@ -256,7 +256,14 @@ templ AudioReader(user User, metadata ReaderMetadata) {
 							</div>
 						</div>
 					</div>
-					<span class="inline-block min-w-[4.75rem] text-right" x-text="fmtTime(chaptersDuration() || 1)">0:00</span>
+					<button
+						type="button"
+						class="inline-block min-w-[4.75rem] text-right cursor-pointer"
+						x-text="endTimeText()"
+						:aria-label="endTimeAria()"
+						:title="endTimeAria()"
+						@click="cycleEndTime()"
+					>0:00</button>
 				</div>
 				<div class="flex items-center justify-center gap-3 md:gap-5">
 					<button