refactor: remove broken anon mode feature

- delete the anon mode hook/store and stop wiring publish flows through alternate signers
  - strip the settings UI, avatar warning, reply indicators, and FAQ text that referenced the toggle
  - drop the anon mode translation keys via scripts/update-translations.js

public/translations/zh/default.json

@@ -221,8 +221,6 @@
   "static_gif": "静态GIF",
   "animated_gif": "动画GIF",
   "hide_avatars": "隐藏头像",
-  "anon_mode": "匿名模式",
-  "anon_mode_description": "为您发布的每个线程使用唯一的用户 ID。这些 ID 无法追溯到您的原始帐户。",
   "pending": "待处理",
   "failed": "失败",
   "add": "添加",
@@ -247,7 +245,6 @@
   "crypto_address_yours": "加密地址属于此帐户。",
   "delete_wallet": "删除钱包",
   "loading_board": "正在加载板块",
-  "avatar_warning": "在匿名模式开启时，您无法使用头像进行发布。您可以在 Plebbit 账户设置中将其关闭。",
   "last_bumped": "最后提升",
   "threads_without_images_tip": "仅显示链接到可嵌入媒体的帖子",
   "hide_gore_boards_tip": "不显示来自带有“gore”标签的板块的帖子",