Reader: visible text selection in every theme; highlights follow across translations

Selection
- Selected text uses a per-theme colour (it was nearly invisible on Dark)
- The colour picker also appears on touch screens after dragging the selection
  handles, and sits below the selection there so the system menu doesn't cover it

Highlights
- Each highlight remembers its translation and whether it covers the whole verse
- In another translation the same words are found again (ignoring case and
  punctuation); whole-verse highlights cover the whole verse; when the wording
  differs, the verse gets a small colour dot instead of marking the wrong words
- Older highlights are checked against their saved words instead of trusted
- Server keeps the new fields

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

src/components/reader/VerseSheet.jsx

@@ -9,6 +9,7 @@ import { READER_TRANSLATIONS, fetchChapter } from '../../utils/bibleText.js';
 import { diffVerses, differenceLabel } from '../../utils/textDiff.js';
 import { DiffText } from './DiffText.jsx';
 import { HIGHLIGHT_COLORS, colorTitle } from '../../utils/highlightColors.js';
+import { isWholeVerse } from '../../utils/highlightSpans.js';
 import { useIqAvailable } from '../../hooks/useIq.js';
 import VerseShareImage from '../VerseShareImage.jsx';
 import IqLexicon from '../iq/IqLexicon.jsx';
@@ -223,7 +224,7 @@ export default function VerseSheet({
         <div className="mb-3 flex flex-wrap items-center gap-1.5" role="group" aria-label="Highlight this verse">
           <span className="mr-1 text-xs text-[var(--r-sub)]">Highlight</span>
           {HIGHLIGHT_COLORS.map((color) => {
-            const on = verseHighlights.some((h) => h.color === color && h.startOffset === 0 && h.endOffset >= verse.text.length);
+            const on = verseHighlights.some((h) => h.color === color && isWholeVerse(h, verse.text));
             return (
               <button key={color} type="button" onClick={() => onHighlightVerse(color)} aria-pressed={on}
                 aria-label={`Highlight verse ${colorTitle(color, colorLabels).toLowerCase()}`} data-tip={`${colorTitle(color, colorLabels)}${on ? ' — tap to remove' : ''}`}