feat(contacts): animated avatars (GIF/WebP) with a Settings toggle

Animate contact avatars end to end:

- texture_loader gains LoadAnimatedRGBA: decodes an image into a downscaled
  RGBA frame sequence + per-frame durations — animated GIF via stb
  (stbi_load_gif_from_memory) and animated WebP via libwebp's WebPAnimDecoder;
  stills (and APNG, which stb reads as one image) return a single frame. Frames
  are box-downscaled (smaller cap for animations) to bound VRAM, capped at 300.
- The contacts avatar cache now holds a frame sequence; currentAvatarFrame()
  advances animated avatars by the ImGui clock and is used everywhere avatars
  draw (list, cards, table, grid, preview). When a live animated frame is drawn
  it flags the render loop (ConsumeContactsAvatarAnimation, clear-on-read) so
  main.cpp keeps producing frames while animation plays and idles when it stops
  or the contacts view is hidden.
- New animate_avatars setting (default on) + a Settings appearance toggle
  ("Animate avatars"); off shows the first frame only. currentAvatarFrame
  honors it. +i18n (8 langs, CJK subset rebuilt for 帧/播/첫).

Verified: a 3-frame GIF and a 3-frame animated WebP both decode to 3 frames
with correct 120ms delays through the exact libwebp/stb calls used here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/zh.json

@@ -54,6 +54,7 @@
     "amount_details": "金额详情",
     "amount_exceeds_balance": "金额超过余额",
     "amount_label": "金额：",
+    "animate_avatars": "动画头像",
     "appearance": "外观",
     "auto_shield": "自动屏蔽挖矿",
     "av_intro": "挖矿软件经常被标记为潜在有害程序。请按照以下步骤启用矿池挖矿：",
@@ -1329,6 +1330,7 @@
     "try_again": "重试",
     "tt_addr_url": "在区块浏览器中查看地址的基础 URL",
     "tt_address_book": "管理已保存的地址以快速发送",
+    "tt_animate_avatars": "播放动画联系人头像（GIF / WebP）；关闭时仅显示第一帧",
     "tt_auto_lock": "在此不活动时间后锁定钱包",
     "tt_auto_shield": "自动将透明余额转移到屏蔽地址以增强隐私",
     "tt_backup": "创建 wallet.dat 的备份",