style(type): raise the too-small toolbar and filter text toward the view-switcher size

The view-switcher's 16px reads comfortably; the toolbar and filter controls sat at 12px. Bring
the marked controls up to match, and lift the general scale on the shared filter surfaces.

- Toolbar (feed + channel + Plex, via the shared components): FilterSelect and SortControl trigger
  pills text-xs → text-base (16px, the view-switcher size); the result count → text-sm; the
  active-filter chips → text-sm with the "FILTERED BY" label text-2xs → text-xs.
- Filterbar: the Combobox picker input → text-base (matching the toolbar pills) + its chips → text-sm;
  the panel/widget headers (SidePanel collapsed-rail + panel title, PanelGroup widget titles) up one step.

Channel info and the manager tables were already at 14–16px (readable), so they were left as-is.

frontend/src/components/Feed.tsx

@@ -617,7 +617,7 @@ export default function Feed({
           </>
         )}
         <span className="mx-1 h-5 w-px bg-border" aria-hidden="true" />
-        <span data-testid="feed-result-count" className="text-xs text-muted whitespace-nowrap">
+        <span data-testid="feed-result-count" className="text-sm text-muted whitespace-nowrap">
           {summaryQuery.data
             ? t("feed.videoCount", {
                 count: summaryQuery.data.count,