polish(layout): tidy filter header + sync status at higher browser zoom

- Filter header: show the active-filter count as a compact number pill instead of
  '{n} active' text, and keep the action buttons on one line (shrink-0 + nowrap) so
  nothing truncates or wraps in a narrow / zoomed-in sidebar (e.g. 125% browser zoom).
- Sync status: anchor the 'all synced' state with a small check icon so it no longer
  reads as orphaned text at the top of the nav rail.

frontend/src/components/Sidebar.tsx

@@ -541,21 +541,24 @@ export default function Sidebar({
           >
             <ChevronLeft className="w-4 h-4" />
           </button>
-          <div className="text-sm font-semibold truncate">
-            {t("sidebar.filters")}
-            {activeCount > 0 && (
-              <span className="ml-1.5 text-xs font-medium text-accent">
-                {t("sidebar.activeCount", { count: activeCount })}
-              </span>
-            )}
-          </div>
+          <span className="text-sm font-semibold shrink-0">{t("sidebar.filters")}</span>
+          {activeCount > 0 && (
+            // Compact count pill (not "{n} active" text) so it never truncates or forces the
+            // action buttons to wrap in a narrow / zoomed-in sidebar.
+            <span
+              title={t("sidebar.activeCount", { count: activeCount })}
+              className="shrink-0 min-w-[18px] h-[18px] px-1.5 rounded-full bg-accent/15 text-accent text-[11px] font-semibold inline-flex items-center justify-center tabular-nums"
+            >
+              {activeCount}
+            </span>
+          )}
         </div>
-        <div className="flex items-center gap-0.5">
+        <div className="flex items-center gap-0.5 shrink-0">
           {!editing && (
             <button
               onClick={clearAll}
               disabled={!active}
-              className="text-xs text-muted enabled:hover:text-accent disabled:opacity-40 transition px-1"
+              className="text-xs text-muted enabled:hover:text-accent disabled:opacity-40 transition px-1 whitespace-nowrap"
             >
               {t("sidebar.clearAll")}
             </button>