v6.8.15: the Android app is out for testing

- Android APK download, served from securebit.chat (/downloads/, never
  committed): a "Download Android APK" badge next to the Snap Store one, drawn
  for both themes, and an Android entry in the download menu (recommended on
  Android devices). nginx serves .apk as an attachment; the service worker
  leaves /downloads/ alone. The APK version is one constant in three places,
  checked by tests/desktop-download-links.test.mjs.
- Roadmap versions follow the real releases: Group Communications v6.0
  shipped, Mobile Edition v6.8 is current, Quantum-Resistant v7.0 is in
  development (2027), then v8.0 and v9.0.
- "Download desktop app" is now "Download the app"; the "You're on Web" pill
  in the download menu is gone.

locales/zh.json

@@ -223,7 +223,7 @@
     ],
     "roadmap.r9.title": "群组通讯",
     "roadmap.r9.sub": "在不牺牲隐私的前提下进行群聊",
-    "roadmap.r9.date": "当前",
+    "roadmap.r9.date": "2026 年秋",
     "roadmap.r9.features": [
       "最多 8 人的 P2P 群聊",
       "网状投递，并以签名中继作为兜底",
@@ -236,7 +236,7 @@
     ],
     "roadmap.r10.title": "Mobile Edition",
     "roadmap.r10.sub": "面向 iOS 与 Android 的原生移动应用",
-    "roadmap.r10.date": "2027 年第二季度",
+    "roadmap.r10.date": "当前",
     "roadmap.r10.features": [
       "iOS 原生应用（Swift/SwiftUI）",
       "Android 原生应用（Kotlin/Jetpack Compose）",
@@ -249,7 +249,7 @@
     ],
     "roadmap.r11.title": "抗量子版本",
     "roadmap.r11.sub": "抵御量子计算机",
-    "roadmap.r11.date": "2027 年第四季度",
+    "roadmap.r11.date": "2027",
     "roadmap.r11.features": [
       "后量子密码学 CRYSTALS-Kyber",
       "SPHINCS+ 数字签名",
@@ -351,7 +351,7 @@
     "action.copy": "复制",
     "action.copied": "已复制",
     "action.scan": "扫描",
-    "action.downloadDesktop": "下载桌面应用",
+    "action.downloadDesktop": "下载应用",
     "action.advancedSettings": "高级设置",
     "cred.reveal": "点击显示 - 请勿泄露此代码",
     "cred.orCopy": "或复制代码",
@@ -646,7 +646,7 @@
     "sec.simulatedWarning": "注意：连接可能尚未完全建立 - 这些数值可能是模拟的。",
     "dl.title": "下载 SecureBit",
     "dl.free": "免费 · 开源",
-    "dl.soon": "移动端应用（iOS、Android）与浏览器扩展（Chrome、Firefox、Opera）即将推出。",
+    "dl.soon": "iOS 应用与浏览器扩展（Chrome、Firefox、Opera）即将推出。",
     "chatHdr.chat": "聊天",
     "chatHdr.chats": "聊天",
     "chatHdr.newChat": "+ 新建",
@@ -795,7 +795,6 @@
     "offline.disconnect": "断开连接",
     "offline.learnMore": "了解更多",
     "pwa.installApp": "安装应用",
-    "chat.onWeb": "你正在使用网页版",
     "groupCall.startVoice": "发起群组语音通话",
     "groupCall.startVideo": "发起群组视频通话",
     "groupCall.join": "加入",