Group Settings into tabs instead of one long scroll

Splits the eleven stacked panel sections into four tabs (Connection,
Audio, Appearance & overlay, System & backup) so a specific setting
is a click away rather than a long scroll, per user feedback. Purely
a layout change - no section's markup, ids, or event bindings moved.

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

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "rc-racecore",
-  "version": "1.11.0",
+  "version": "1.12.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "rc-racecore",
-      "version": "1.11.0",
+      "version": "1.12.0",
       "hasInstallScript": true,
       "dependencies": {
         "better-sqlite3": "^12.11.1",