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/fr.json

@@ -54,6 +54,7 @@
     "amount_details": "DÉTAILS DU MONTANT",
     "amount_exceeds_balance": "Le montant dépasse le solde",
     "amount_label": "Montant :",
+    "animate_avatars": "Animer les avatars",
     "appearance": "APPARENCE",
     "auto_shield": "Auto-blindage du minage",
     "av_intro": "Les logiciels de minage sont souvent signalés comme potentiellement indésirables. Suivez ces étapes pour activer le minage en pool :",
@@ -1329,6 +1330,7 @@
     "try_again": "Réessayer",
     "tt_addr_url": "URL de base pour consulter les adresses dans un explorateur de blocs",
     "tt_address_book": "Gérer les adresses enregistrées pour un envoi rapide",
+    "tt_animate_avatars": "Lit les avatars de contact animés (GIF / WebP) ; désactivé n'affiche que la première image",
     "tt_auto_lock": "Verrouiller le portefeuille après cette durée d'inactivité",
     "tt_auto_shield": "Déplacer automatiquement le solde transparent vers des adresses blindées pour la confidentialité",
     "tt_backup": "Créer une sauvegarde de votre wallet.dat",