Fit the whole top bar on one row

Timer, day arrows, date picker and Today all share a single non-wrapping
row: the timer slims to 1rem, buttons and gaps tighten, arrows sit
around the picker, and a narrow-phone media query compacts further.

src/index.html

@@ -86,8 +86,8 @@
         </div>
         <button type="button" id="day-prev" class="ghost" aria-label="Previous day">←</button>
         <input type="date" id="day-picker" />
-        <button type="button" id="day-today" class="ghost">Today</button>
         <button type="button" id="day-next" class="ghost" aria-label="Next day">→</button>
+        <button type="button" id="day-today" class="ghost">Today</button>
       </section>
 
       <section class="quick-actions">