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/ja.json

@@ -54,6 +54,7 @@
     "amount_details": "金額の詳細",
     "amount_exceeds_balance": "金額が残高を超えています",
     "amount_label": "金額：",
+    "animate_avatars": "アバターをアニメーション",
     "appearance": "外観",
     "auto_shield": "マイニング自動シールド",
     "av_intro": "マイニングソフトウェアは、望ましくない可能性があるものとしてフラグが立てられることがよくあります。プールマイニングを有効にするには、次の手順に従ってください。",
@@ -1329,6 +1330,7 @@
     "try_again": "再試行",
     "tt_addr_url": "ブロックエクスプローラーでアドレスを表示するためのベース URL",
     "tt_address_book": "クイック送信用の保存済みアドレスを管理",
+    "tt_animate_avatars": "アニメーション連絡先アバター（GIF / WebP）を再生。オフでは最初のフレームのみ表示",
     "tt_auto_lock": "この無操作時間後にウォレットをロック",
     "tt_auto_shield": "プライバシーのため透明残高を自動的にシールドアドレスに移動",
     "tt_backup": "wallet.dat のバックアップを作成",