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/ui/pages/settings_page.cpp

@@ -899,6 +899,16 @@ void RenderSettingsPage(App* app) {
                 }
                 if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_theme_effects"));
 
+                ImGui::SameLine(0, Layout::spacingLg());
+                {
+                    bool anim = app->settings()->getAnimateAvatars();
+                    if (ImGui::Checkbox(TrId("animate_avatars", "animate_avatars").c_str(), &anim)) {
+                        app->settings()->setAnimateAvatars(anim);
+                        app->settings()->save();
+                    }
+                    if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_animate_avatars"));
+                }
+
                 // Console output color toggles (own row — no GPU cost, enabled even in low-spec).
                 renderConsoleColorToggles(app);
 
@@ -1154,6 +1164,16 @@ void RenderSettingsPage(App* app) {
                 }
                 if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_theme_effects"));
 
+                ImGui::SameLine(0, Layout::spacingLg());
+                {
+                    bool anim = app->settings()->getAnimateAvatars();
+                    if (ImGui::Checkbox(TrId("animate_avatars", "animate_avatars").c_str(), &anim)) {
+                        app->settings()->setAnimateAvatars(anim);
+                        app->settings()->save();
+                    }
+                    if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_animate_avatars"));
+                }
+
                 // Console output color toggles (own row — no GPU cost, enabled even in low-spec).
                 renderConsoleColorToggles(app);