feat(plex): subtitles rise above the control bar while it shows

On an iPad the bar covered the text whenever it was up: the browser places a
native cue by its line, which nothing animates. The track now stays loaded as
hidden and PlexSubtitles draws the active cues, measured against the bar and
lifted above it in 200 ms, back down when it hides. The viewer's size, colour,
background and outline settings style the text directly. Also fixes a test
typing slip from the search pill change.

frontend/src/components/SearchBar.dom.test.tsx

@@ -42,7 +42,14 @@ describe("SearchBar on a touch screen", () => {
 
   it("shortens Go to its icon by the column's width, not the screen's", () => {
     const { getByText } = render(
-      <SearchBar value="" onChange={() => {}} onGo={() => {}} goIcon={<svg />} goLabel="Go far" />,
+      <SearchBar
+        value=""
+        onChange={() => {}}
+        placeholder="Search…"
+        onGo={() => {}}
+        goIcon={<svg />}
+        goLabel="Go far"
+      />,
     );
     const label = getByText("Go far");
     expect(label.className).toContain("@min-[900px]/appmain:inline");