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>

src/config/settings.cpp

@@ -176,6 +176,7 @@ bool Settings::load(const std::string& path)
         if (portfolio_style_ < 0 || portfolio_style_ > 2) portfolio_style_ = 0;
         loadScalar(j, "contacts_view_mode", contacts_view_mode_);
         if (contacts_view_mode_ < 0 || contacts_view_mode_ > 2) contacts_view_mode_ = 0;
+        loadScalar(j, "animate_avatars", animate_avatars_);
         loadScalar(j, "scanline_enabled", scanline_enabled_);
         loadScalar(j, "console_line_accents", console_line_accents_);
         loadScalar(j, "console_text_color", console_text_color_);
@@ -431,6 +432,7 @@ bool Settings::save(const std::string& path)
     j["balance_layout"] = balance_layout_;  // saved as string ID
     j["portfolio_style"] = portfolio_style_;
     j["contacts_view_mode"] = contacts_view_mode_;
+    j["animate_avatars"] = animate_avatars_;
     j["scanline_enabled"] = scanline_enabled_;
     j["console_line_accents"] = console_line_accents_;
     j["console_text_color"] = console_text_color_;