Repaint the whole tree viewport while scrolling

The right-aligned icon strip is positioned against the viewport rather than
the row, so the pixels a blit scroll reuses are stale and the icons leave
ghosts behind. Scroll the viewport in simple mode, and widen every repaint
request to the full visible width so a row whose label changes size cannot
leave its icons behind either.

Also stop blacklisting an icon whose download failed only because the file
transfer channel was not up yet: channel rows are painted during connect,
well before that point, so their icons would never be retried.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ts3-client/core/src/main/java/com/ts3client/net/IconRepository.java

@@ -118,6 +118,9 @@ public final class IconRepository {
             icons.put(id, data);
             writeDiskCache(id, data);
             if (onIconLoaded != null) onIconLoaded.run();
+        } catch (IllegalStateException e) {
+            // Not connected (yet): a channel icon can be asked for while the tree is
+            // first painted, before file transfers are up. Leave it retryable.
         } catch (Exception e) {
             // Missing or permission-denied icons are common; don't ask again.
             failed.add(id);