Fix log viewer on small screens

Previously it showed a lot of white space at the bottom, and the floating box
didn't stick. Both is now fixed.

AI-assistant: Copilot v1.0.7 (Claude Sonnet 4.6)

Signed-off-by: Pablo Zmdl <pablo@nextcloud.com>

php/public/log-view.js

@@ -96,7 +96,7 @@ class LogViewer {
     }
 
     scrollToBottom() {
-        window.scrollTo(0, document.body.scrollHeight);
+        this.logElem.scrollTop = this.logElem.scrollHeight;
     }
 
     initAutoloadingControls() {