feat: Placeholder farbig markieren in Freigabe-View und Pair-Modal

Objekt-Placeholder indigo, Wort-Placeholder grün, geleakte ⟦PHn⟧-Tokens rot.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/PairReviewModal.jsx

@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { apiPost, apiPatch } from '../lib/api';
 import { buildRows } from '../lib/pairRows';
+import PlaceholderText from './PlaceholderText';
 
 const LANGS = [
   { code: 'de', flag: '🇩🇪' },
@@ -130,7 +131,7 @@ function Row({ row }) {
         const val = row.cell(l.code);
         return (
           <div key={l.code} className={`text-sm rounded-lg border px-2.5 py-1.5 ${val ? `bg-slate-50 border-slate-200 ${row.color}` : 'bg-red-50 border-red-200 text-red-400 italic'}`}>
-            {val || 'fehlt'}
+            {val ? <PlaceholderText text={val} /> : 'fehlt'}
           </div>
         );
       })}

src/components/PlaceholderText.jsx

@@ -0,0 +1,29 @@
+import { parsePlaceholderSegments } from '../lib/pairRows';
+
+// Rendert Satztext mit farbig markierten Placeholdern:
+//  {{label.o:id}} → indigo (Objekt-Verknüpfung, passend zu den 🔗-Buttons)
+//  {{label.w:id}} → emerald (Wort-Verknüpfung)
+//  ⟦PHn:label⟧    → rot (geleaktes Übersetzungs-Token, Datenfehler)
+const KIND_STYLES = {
+  object: { className: 'bg-indigo-100 text-indigo-800 rounded px-0.5', title: 'Objekt-Placeholder' },
+  word:   { className: 'bg-emerald-100 text-emerald-800 rounded px-0.5', title: 'Wort-Placeholder' },
+  broken: { className: 'bg-red-100 text-red-700 rounded px-0.5 line-through', title: 'Kaputtes Übersetzungs-Token — bitte reparieren' },
+};
+
+export default function PlaceholderText({ text }) {
+  const segs = parsePlaceholderSegments(text);
+  return (
+    <>
+      {segs.map((s, i) => {
+        const style = s.kind && KIND_STYLES[s.kind];
+        if (!style) return <span key={i}>{s.text}</span>;
+        return (
+          <mark key={i} className={style.className}
+            title={`${style.title}${s.id ? ` · ${s.id.slice(0, 8)}…` : ''}`}>
+            {s.text}
+          </mark>
+        );
+      })}
+    </>
+  );
+}