Make the app work better on iPhone and iPad

- Text fields are at least 16px on touch screens (stops iOS zooming on focus)
- Chapter swipe ignores sheets, fields, sliders, sideways-scrolling rows and text selection
- vh -> dvh for sheets, palette and dialogs
- Bigger tap targets for small links, chips and the logo; no double-tap delay
- No tap flash or landscape text inflation

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/components/reader/Sheet.jsx

@@ -46,7 +46,7 @@ export default function Sheet({ open, onClose, title, label, headerRight, modal
         aria-modal={modal ? 'true' : undefined}
         aria-label={typeof title === 'string' ? title : label}
         tabIndex={-1}
-        className={`fixed inset-x-0 bottom-0 z-50 flex max-h-[72vh] flex-col rounded-t-2xl focus:outline-none border-t border-[var(--r-line)] bg-[var(--r-bar)] text-[var(--r-text)] font-sans ${
+        className={`fixed inset-x-0 bottom-0 z-50 flex max-h-[72dvh] flex-col rounded-t-2xl focus:outline-none border-t border-[var(--r-line)] bg-[var(--r-bar)] text-[var(--r-text)] font-sans ${
           pane ? 'lg:inset-x-auto lg:bottom-0 lg:right-0 lg:top-12 lg:max-h-none lg:w-[var(--reader-pane,24rem)] lg:rounded-none lg:border-l lg:border-t-0' : 'sm:left-1/2 sm:right-auto sm:w-[36rem] sm:-translate-x-1/2'
         }`}
       >