Stop the page extending under the status bar; use visible-viewport units

Drops viewport-fit=cover so the iPad/iPhone status bar is its own area and the system's
top-edge blur no longer covers the app bar. Fixed-height study stages are position:fixed so
they cannot scroll the document, and min-h-screen/100vh become dvh units.

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

src/pages/ReaderPage.jsx

@@ -328,7 +328,7 @@ export default function ReaderPage() {
   const paneOpen = !!selectedVerse && !readerDrawMode;
 
   return (
-    <div className="min-h-screen bg-[var(--r-bg)] text-[var(--r-text)]" style={themeVars(readerTheme)}
+    <div className="min-h-dvh bg-[var(--r-bg)] text-[var(--r-text)]" style={themeVars(readerTheme)}
          onTouchStart={handleTouchStart} onTouchEnd={handleTouchEnd}>
       {chromeVisible && (
         <TopBar