feat!: remove the shared demo account

The demo account — one shared user that whitelisted emails entered from
the login page, reset on a schedule — goes end to end (owner decision,
E34): demo.py and the reset job, users.is_demo and demo_whitelist
(migration 0098 deletes the demo user, its audit rows, the reset job's
override and notices, then drops the column and table; the downgrade
restores the empty schema), the /auth/demo entry, the admin whitelist and
reset, the Demo tab, the banner, the login page's "Try the demo", and
every is_demo branch in routes, userscope, scheduler and the UI.

require_human only ever refused the demo account, so its 87 uses become
current_user (owner-approved); require_write_scope keeps its own check.
The login page's "or" divider now shows only beside the Google button:
without the demo entry under it, an instance without Google would have
said "or" to nothing.

A contract test (removedFeatures) fails on the word anywhere in the
backend, frontend, e2e or scripts — seen red on a planted hit. Size
ceilings tightened for the modules that shrank; admin.py is back under
the limit.

frontend/src/components/PlexSidebar.tsx

@@ -20,7 +20,6 @@ import SavedViewsPopover from "./SavedViewsPopover";
 import PersonalViewsModal from "./PersonalViewsModal";
 import { useSavedViews } from "./savedViewsContext";
 import { usePlex, usePlexActions } from "./plexContext";
-import { useMe } from "../lib/useMe";
 import { DismissibleChip } from "./ui/Chip";
 import { Input } from "./ui/Input";
 
@@ -51,9 +50,8 @@ 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.
+  // title opens the full manager modal (same shared components as the feed).
   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.
@@ -314,15 +312,11 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
         // 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")}
+        // Saved ("personal") views: header icon → quick-pick popover, title → the manager modal.
+        // Same shared components as the feed rail (SavedViewsProvider switches source).
+        iconExpanded={<SavedViewsPopover trigger={<SlidersHorizontal className="w-4 h-4" />} />}
+        onTitleClick={openModal}
+        titleActionLabel={t("views.manageTitle")}
       />
       {/* The manager modal lives here (rail is always mounted on plex); Modal portals to <body>. */}
       {modalOpen && <PersonalViewsModal />}