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/util/texture_loader.h

@@ -6,9 +6,31 @@
 
 #include "imgui.h"
 
+#include <vector>
+
 namespace dragonx {
 namespace util {
 
+/**
+ * @brief Downscaled RGBA frame sequence for an image (1 frame for stills, N for animations).
+ */
+struct AnimFrames {
+    std::vector<std::vector<unsigned char>> frames;  ///< each is w*h*4 RGBA (already downscaled)
+    std::vector<float> delaysSec;                    ///< per-frame duration in seconds (parallel to frames)
+    int w = 0;
+    int h = 0;
+};
+
+/**
+ * @brief Decode an image into 1+ downscaled RGBA frames plus per-frame durations.
+ *
+ * Animated GIF (via stb) and animated WebP (via libwebp WebPAnimDecoder) return every frame (capped at
+ * maxFrames); static formats — and APNG, which stb reads as a single image — return one frame. Frames
+ * are box-downscaled internally (smaller for animations to bound VRAM). The caller uploads each frame
+ * with CreateRawTexture. Returns false on decode failure.
+ */
+bool LoadAnimatedRGBA(const char* path, int maxFrames, AnimFrames& out);
+
 /**
  * @brief Load a PNG/JPG/BMP image from disk into an OpenGL or DX11 texture.
  * @param path  File path (relative to working directory or absolute)