Show client avatars and let the user set their own

Avatars are fetched from the server's file repository as /avatar_<id>,
verified against client_flag_avatar and cached on disk; animated GIFs play in
the info panel. Self > Set avatar... uploads or removes our own picture within
the server's size limit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/AvatarView.java

@@ -0,0 +1,65 @@
+package com.ts3client.ui;
+
+import javax.swing.JComponent;
+import java.awt.Dimension;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.Image;
+import java.awt.RenderingHints;
+import java.awt.Toolkit;
+
+/**
+ * Paints an avatar scaled to fit, keeping its aspect ratio. The image is a Toolkit
+ * image drawn with this component as its observer, so an animated GIF keeps playing:
+ * each decoded frame triggers a repaint.
+ */
+final class AvatarView extends JComponent {
+
+    private final int boxSize;
+    private Image image;
+    private int imageWidth = -1;
+    private int imageHeight = -1;
+
+    AvatarView(int boxSize) {
+        this.boxSize = boxSize;
+        setPreferredSize(new Dimension(boxSize, boxSize));
+        setMinimumSize(getPreferredSize());
+    }
+
+    /** @param data the encoded image, or {@code null} to show nothing */
+    void setImage(byte[] data) {
+        if (image != null) image.flush();
+        image = data == null ? null : Toolkit.getDefaultToolkit().createImage(data);
+        imageWidth = imageHeight = -1;
+        repaint();
+    }
+
+    boolean hasImage() {
+        return image != null;
+    }
+
+    @Override
+    protected void paintComponent(Graphics g) {
+        if (image == null) return;
+        if (imageWidth < 0 || imageHeight < 0) {
+            // Unknown until the header is decoded; the observer repaints once it is.
+            imageWidth = image.getWidth(this);
+            imageHeight = image.getHeight(this);
+            if (imageWidth < 0 || imageHeight < 0) return;
+        }
+        double scale = Math.min(1.0, Math.min((double) getWidth() / imageWidth, (double) getHeight() / imageHeight));
+        int w = Math.max(1, (int) Math.round(imageWidth * scale));
+        int h = Math.max(1, (int) Math.round(imageHeight * scale));
+        Graphics2D g2 = (Graphics2D) g.create();
+        try {
+            g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
+            g2.drawImage(image, (getWidth() - w) / 2, (getHeight() - h) / 2, w, h, this);
+        } finally {
+            g2.dispose();
+        }
+    }
+
+    int boxSize() {
+        return boxSize;
+    }
+}