feat(tauri): update Windows taskbar badge with combined count

The Windows overlay badge now renders a single combined number and
includes an additional “changes” component in the total. This makes
the badge more informative while keeping the icon compact and
legible across small sizes.

- Simplify badge rendering to one circle with centered text
- Extend the Tauri command and frontend call to pass changes count

src/App.svelte

@@ -679,7 +679,7 @@
       repoPath = "";
       status = null;
       lastStatusFingerprint = "";
-      void setSyncBadge(0, 0).catch(() => {});
+      void setSyncBadge(0, 0, 0).catch(() => {});
     }
     branches = [];
     commits = [];
@@ -713,7 +713,7 @@
     repoPath = activeRepoPath;
     lastStatusFingerprint = statusFingerprint(nextStatus);
     upsertRepoTab(activeRepoPath, nextStatus);
-    void setSyncBadge(nextStatus.ahead, nextStatus.behind).catch(() => {});
+    void setSyncBadge(nextStatus.ahead, nextStatus.behind, nextStatus.files.length).catch(() => {});
   }
 
   function errorToMessage(error: unknown): string {