feat(plex): port the saved-views (personal views) UI to Plex (frontend)

Plex now has the same personal-views system as the feed — the rail header icon
opens the quick-pick popover, the rail title opens the manager modal (list /
create / rename / delete / reorder / set-default / apply), and the active view
leads the chip row with a "modified" dot.

One SavedViewsProvider serves both modules: it switches `source` (feed ⟷ plex)
by the active page (both filter providers are global, so it reads whichever the
page owns) and runs the same logic on per-source wiring — the live filters,
apply, a stable signature (feed filtersToParams / plex plexFiltersSignature),
coercion (asFilters / coercePlexFilters), and what to strip on save. Moved below
PlexProvider in the tree so it can read plex state; resets sticky/modal on a
source switch. The shared popover/modal/chip are unchanged; the modal describes
a plex view's captured filters via a pure buildPlexActiveFilters (extracted from
usePlexActiveFilters — no duplication). api.savedViews/createView take a source;
`SavedView.filters` is now an opaque blob. New coercePlexFilters/plexFilters-
Signature (also dedups PlexProvider's collection migration). Empty-state copy
genericised (no longer says "feed"). A Plex view captures the rail filters (not
watch-state/sort/scope).

Verified end-to-end on localdev: create/apply/preview/default/delete on plex,
feed views stay separate + unregressed (402 vitest), no console errors.

frontend/src/components/PlexSidebar.tsx

@@ -13,7 +13,11 @@ import { type PanelItem } from "./PanelGroups";
 import SegmentedToggle from "./SegmentedToggle";
 import FilterChipGroup from "./FilterChipGroup";
 import Combobox, { type ComboboxOption } from "./Combobox";
+import SavedViewsPopover from "./SavedViewsPopover";
+import PersonalViewsModal from "./PersonalViewsModal";
+import { useSavedViews } from "./SavedViewsProvider";
 import { usePlex, usePlexActions } from "./PlexProvider";
+import { useMe } from "../lib/useMe";
 
 // The Plex module's left filter column — now the shared floating SidePanel with its filter groups
 // as reorderable "islands" (same system as the feed rail). Movie libraries get the full metadata
@@ -66,6 +70,10 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
   // hand-off to PlexBrowse via the shared `playlistOpen` slot.
   const { scope, show, filters } = usePlex();
   const { setFilters } = usePlexActions();
+  const isDemo = useMe().is_demo;
+  // Personal ("saved") views for the Plex module: the rail header icon opens a quick-pick popover, the
+  // title opens the full manager modal (same shared components as the feed). Hidden for the demo account.
+  const { openModal, modalOpen } = useSavedViews();
   // This rail's media source (the Plex library) — names the abstraction the feed and Plex rails
   // share; drives the panel layout key. `FilterRail` owns the customize `editing` state now.
   const source: MediaSourceKind = "plex";
@@ -291,20 +299,33 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
   ];
 
   return (
-    <FilterRail
-      kind={source}
-      title={t("sidebar.filters")}
-      icon={<SlidersHorizontal className="w-4 h-4" />}
-      count={activeCount}
-      collapsed={collapsed}
-      onToggleCollapse={onToggleCollapse}
-      layout={layout}
-      setLayout={setLayout}
-      items={items}
-      // The Plex widgets are simple label + control rows now, not collapsible islands (matches the
-      // feed rail). The rail's own "Clear all" is dropped too — the chip row above the grid owns it.
-      collapsible={false}
-    />
+    <>
+      <FilterRail
+        kind={source}
+        title={t("sidebar.filters")}
+        icon={<SlidersHorizontal className="w-4 h-4" />}
+        count={activeCount}
+        collapsed={collapsed}
+        onToggleCollapse={onToggleCollapse}
+        layout={layout}
+        setLayout={setLayout}
+        items={items}
+        // The Plex widgets are simple label + control rows now, not collapsible islands (matches the
+        // feed rail). The rail's own "Clear all" is dropped too — the chip row above the grid owns it.
+        collapsible={false}
+        // Saved ("personal") views: header icon → quick-pick popover, title → the manager modal. Hidden
+        // for the demo account. Same shared components as the feed rail (SavedViewsProvider switches source).
+        iconExpanded={
+          isDemo ? undefined : (
+            <SavedViewsPopover trigger={<SlidersHorizontal className="w-4 h-4" />} />
+          )
+        }
+        onTitleClick={isDemo ? undefined : openModal}
+        titleActionLabel={isDemo ? undefined : t("views.manageTitle")}
+      />
+      {/* The manager modal lives here (rail is always mounted on plex); Modal portals to <body>. */}
+      {modalOpen && <PersonalViewsModal />}
+    </>
   );
 }