refactor(frontend): the flat components/ folder moves into shell/, modules/<page>/ and features/<name>/

A pure move (git mv, history kept): 333 files leave components/, which now holds only the platform
layer (ui/) and the legal pages. The shell is the frame (App, header, nav rail, palette, boot); each
page lives in modules/<page>/ with its rail, store and tests; what several pages share sits in
features/<name>/; the shared-link page is watch/. Domain-free helpers went straight to ui/
(ViewSwitcher, FilterRail, the confirm dialog, the language switcher, the copy rows).

Every relative specifier was rewritten (imports, dynamic imports, vi.mock, new URL), and the
contract tests that scan sources now scan the whole app source, not only components/ — each glob
was counted before and after so none went green over fewer files. The locale-format rule matched
`/src/components/` only, so the move would have taken ~300 files out from under its i18n-singleton
check; it now covers every folder that holds components, with a test per folder.

frontend/src/modules/plex/PlexViewToggle.tsx

@@ -0,0 +1,30 @@
+import { useTranslation } from "react-i18next";
+import SegmentedToggle from "../../components/ui/SegmentedToggle";
+import { usePlexViewControls } from "./plexViewContext";
+
+// The Discover ⟷ Browse switch, hosted in the header next to the library-scope pill (All/Movies/Shows).
+// It reflects + drives PlexBrowse's top-level sub-view through the PlexViewBridge, and hides itself on
+// the deeper views (a show/info/person page has no Discover/Browse choice).
+export default function PlexViewToggle() {
+  const { t } = useTranslation();
+  const ctl = usePlexViewControls();
+  // Only the two title-browse views host the Discover/Browse choice; deeper views (show/info/person/…)
+  // and the playlists/collections browse surfaces hide it.
+  if (!ctl || (ctl.kind !== "discover" && ctl.kind !== "grid")) return null;
+  // The floating header wrapper is pointer-events-none (so clicks fall through its empty area to the
+  // content below); every interactive child must re-enable pointer events or it is click-dead — the
+  // sibling PlexScopeToggle does the same.
+  return (
+    <SegmentedToggle
+      size="md"
+      className="pointer-events-auto shrink-0"
+      ariaLabel={t("plex.view.label")}
+      options={[
+        { value: "discover", label: t("plex.discover.tab") },
+        { value: "grid", label: t("plex.view.browse") },
+      ]}
+      value={ctl.kind === "discover" ? "discover" : "grid"}
+      onChange={(v) => ctl.open(v === "discover" ? { kind: "discover" } : { kind: "grid" })}
+    />
+  );
+}