Complete missing Chinese translation keys

[XXXBusy]

Refs #13

Summary

• Completes the missing Simplified Chinese translation keys in src/i18n/translations/zh.json
• Adds translations for theme color, XKR buy/sell, node picker labels, splash words, reaction hint, and feed unread-message labels
• Keeps the existing Chinese translation file structure unchanged

Verification

node - <<'NODE'
const fs=require('fs');
const base='src/i18n/translations';
function loadJsonc(file){
  let s=fs.readFileSync(file,'utf8');
  s=s.replace(/^\s*\/\/.*$/mg,'');
  s=s.replace(/,\s*\/\/[^\n]*/g, ',');
  s=s.replace(/"\s*\/\/[^\n]*/g, '"');
  return JSON.parse(s);
}
function placeholders(value){
  return [...String(value).matchAll(/{{\s*([^}]+?)\s*}}/g)].map(m=>m[1].trim()).sort();
}
const en=loadJsonc(`${base}/en.json`);
const zh=JSON.parse(fs.readFileSync(`${base}/zh.json`,'utf8'));
const enKeys=Object.keys(en);
const zhKeys=Object.keys(zh);
const missing=enKeys.filter(k=>!(k in zh));
const extra=zhKeys.filter(k=>!(k in en));
const placeholderMismatch=enKeys.filter(k=>k in zh && JSON.stringify(placeholders(en[k])) !== JSON.stringify(placeholders(zh[k])));
console.log(JSON.stringify({en:enKeys.length, zh:zhKeys.length, missing, extra, placeholderMismatch}, null, 2));
if (missing.length || extra.length || placeholderMismatch.length) process.exit(1);
NODE

Result:

{
  "en": 139,
  "zh": 139,
  "missing": [],
  "extra": [],
  "placeholderMismatch": []
}

Translation note

The Chinese lines were reviewed for app context before submission.

XKR address

SEKReYxQRcuPYYXgPbGq9oZsEX87oawWUTjdSY5dJ5n6QUw3PTqwJGudF3cMpEup7SVj69D2QvJK4RGKegRjJUZdfQsEr8yvkdr9a00dbd98be5fcf3c1ec4f88f16351d30f96ddf4f056ade9d226ccc78173a507

[XXXBusy]

Validation update:

• Ran a translation key parity check against en.json.
• enKeys: 139, zhKeys: 139.
• Missing keys: none.
• Extra keys: none.

Note on newMessage / newMessages: Chinese does not need a different suffix here because the UI already renders the count before the translated string, so both become natural output like 1 条新消息 and 2 条新消息.