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/ko.json

@@ -54,6 +54,7 @@
     "amount_details": "금액 상세",
     "amount_exceeds_balance": "금액이 잔액을 초과합니다",
     "amount_label": "금액:",
+    "animate_avatars": "아바타 애니메이션",
     "appearance": "외관",
     "auto_shield": "채굴 자동 차폐",
     "av_intro": "채굴 소프트웨어는 종종 잠재적으로 원치 않는 항목으로 표시됩니다. 풀 채굴을 활성화하려면 다음 단계를 따르세요:",
@@ -1329,6 +1330,7 @@
     "try_again": "다시 시도",
     "tt_addr_url": "블록 탐색기에서 주소를 보기 위한 기본 URL",
     "tt_address_book": "빠른 전송을 위해 저장된 주소 관리",
+    "tt_animate_avatars": "애니메이션 연락처 아바타(GIF / WebP) 재생, 끄면 첫 프레임만 표시",
     "tt_auto_lock": "이 비활성 시간 후 지갑 잠금",
     "tt_auto_shield": "개인 정보 보호를 위해 투명 잔액을 자동으로 차폐 주소로 이동",
     "tt_backup": "wallet.dat 백업 만들기",