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/PresentMode.jsx

@@ -106,14 +106,14 @@ export default function PresentMode({ title, subtitle = '', mode, script = '', t
       </div>
 
       {mode === 'script' ? (
-        <div ref={scroller} className="min-h-0 flex-1 overflow-y-auto px-[6vw] py-[8vh]" style={{ scrollBehavior: 'auto' }}>
+        <div ref={scroller} className="min-h-0 flex-1 overflow-y-auto px-[6vw] py-[8dvh]" style={{ scrollBehavior: 'auto' }}>
           {script.trim()
-            ? <div className="mx-auto max-w-[46em] whitespace-pre-wrap font-serif" style={{ fontSize, lineHeight: 1.5 }}>{script}<div style={{ height: '50vh' }} aria-hidden="true" /></div>
+            ? <div className="mx-auto max-w-[46em] whitespace-pre-wrap font-serif" style={{ fontSize, lineHeight: 1.5 }}>{script}<div style={{ height: '50dvh' }} aria-hidden="true" /></div>
             : <p className="mt-20 text-center text-lg opacity-70">There’s no script to present yet. Write one on the Script page.</p>}
         </div>
       ) : (
         <div className="flex min-h-0 flex-1 flex-col">
-          <div className="min-h-0 flex-1 overflow-y-auto px-[6vw] py-[6vh]">
+          <div className="min-h-0 flex-1 overflow-y-auto px-[6vw] py-[6dvh]">
             {step ? (
               <div className="mx-auto max-w-[46em] font-serif" style={{ fontSize, lineHeight: 1.4 }}>
                 <p className="font-sans text-[0.4em] uppercase tracking-[0.16em] opacity-60">{step.kind ? `${step.kind} · ` : ''}Point {index + 1} of {steps.length}{step.minutes ? ` · ${step.minutes} min` : ''}</p>