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/de.json

@@ -54,6 +54,7 @@
     "amount_details": "BETRAGSDETAILS",
     "amount_exceeds_balance": "Betrag übersteigt Guthaben",
     "amount_label": "Betrag:",
+    "animate_avatars": "Avatare animieren",
     "appearance": "ERSCHEINUNGSBILD",
     "auto_shield": "Mining automatisch abschirmen",
     "av_intro": "Mining-Software wird oft als potenziell unerwünscht eingestuft. Führen Sie diese Schritte aus, um das Pool-Mining zu aktivieren:",
@@ -1329,6 +1330,7 @@
     "try_again": "Erneut versuchen",
     "tt_addr_url": "Basis-URL zum Anzeigen von Adressen in einem Block-Explorer",
     "tt_address_book": "Gespeicherte Adressen für schnelles Senden verwalten",
+    "tt_animate_avatars": "Animierte Kontakt-Avatare (GIF / WebP) abspielen; aus zeigt nur das erste Bild",
     "tt_auto_lock": "Wallet nach dieser Inaktivitätszeit sperren",
     "tt_auto_shield": "Transparentes Guthaben automatisch an geschirmte Adressen für Datenschutz verschieben",
     "tt_backup": "Eine Sicherungskopie Ihrer wallet.dat erstellen",