refactor: remove NFT avatar functionality

Removes avatar-settings component, avatar-visibility store, and all
avatar rendering from posts. Strips avatar from account JSON, renames
NFT gateway label to media IPFS gateway, removes Polygon RPC and
hide-avatars toggle. Deletes 6 avatar-related translation keys.

public/translations/zh/default.json

@@ -78,7 +78,6 @@
   "show": "显示",
   "saved": "已保存",
   "paste_signature": "粘贴签名",
-  "chain_ticker": "区块链标记",
   "wallet_address": "钱包地址",
   "copy": "复制",
   "copied": "已复制",
@@ -173,10 +172,7 @@
   "user_banned": "用户因此帖子被禁止",
   "replies": "回复",
   "links": "链接",
-  "avatar": "头像",
-  "token_address_whitelist": "代币地址（<1>仅限白名单</1>）",
   "animated_gif": "动画GIF",
-  "hide_avatars": "隐藏头像",
   "pending": "待处理",
   "failed": "失败",
   "add": "添加",
@@ -198,7 +194,6 @@
   "last_bumped": "最后提升",
   "fit_expanded_images_to_screen": "适应扩展图像到屏幕",
   "fit_expanded_images_to_screen_tip": "将扩展图像限制为浏览器的宽度和高度",
-  "hide_avatars_tip": "不显示用户显示名称旁边的头像",
   "choose_file": "选择文件",
   "uploading": "正在上传...",
   "no_file_chosen": "未选择任何文件",
@@ -231,7 +226,6 @@
   "moderator_of_this_board": "此用户是此版块的版主",
   "administrator_of_this_board": "此用户是此版块的管理员",
   "copy_content_id": "复制内容ID",
-  "delete_avatar": "删除头像",
   "updates": "更新",
   "downloading_board": "正在下载论坛",
   "subscriptions_subtitle": "您已订阅 {{count}} 个 boards",