feat(feed): saved views as a header popover + Personal Views modal + a view chip

Retire the standalone 'Saved views' sidebar panel. The saved-views feature now
lives in three lighter surfaces, coordinated by a new SavedViewsProvider (query +
CRUD + the active/sticky view + modal state):

- the filter panel's header ICON opens a quick-pick popover (apply a view, active
  one checked, plus 'Manage views…');
- the header TITLE ('Filters') opens a new Personal Views modal — a master/detail
  manager: left = the reorderable list + a save-current-filters input, right = the
  selected view's name, its captured filters (shown as the same chips the toolbar
  row uses), default toggle, apply, and delete;
- a SelectedViewChip leads the applied-filter row, naming the active view with a
  warn-coloured 'modified' dot once the live filters diverge from it; clicking it
  reopens the picker.

SidePanel/FilterRail gain optional iconExpanded + onTitleClick slots (feed-only,
hidden for the demo account); the collapsed tab keeps its plain pin behaviour.
SavedViewsWidget is deleted and dropped from the panel layout.

Verified live: icon popover lists HH + Manage; applying HH surfaces the chip and
switches scope; removing a filter lights the dirty dot; the title opens the
master/detail modal with the captured-filters summary. 374 vitest, tsc, eslint
(0 err).

frontend/src/components/SidePanel.tsx

@@ -20,6 +20,8 @@ export default function SidePanel({
   onReset,
   editHint,
   actions,
+  iconExpanded,
+  onTitleClick,
   children,
 }: {
   title: string;
@@ -34,6 +36,11 @@ export default function SidePanel({
   editHint?: string;
   // Extra header controls shown when NOT editing (e.g. the feed's Clear all + Share view).
   actions?: ReactNode;
+  // Optional override for the icon in the EXPANDED header only (the collapsed tab keeps the plain
+  // `icon`) — the feed passes its saved-views popover trigger here so the header icon opens the picker.
+  iconExpanded?: ReactNode;
+  // When set, the expanded-header title becomes a button (the feed opens its Personal Views modal).
+  onTitleClick?: () => void;
   children: ReactNode;
 }) {
   const { t } = useTranslation();
@@ -99,10 +106,19 @@ export default function SidePanel({
             >
               {pinned ? <PinOff className="w-4 h-4" /> : <Pin className="w-4 h-4" />}
             </button>
-            <span className="shrink-0 flex text-accent">{icon}</span>
-            <span className="flex-1 min-w-0 truncate text-sm font-bold uppercase tracking-[0.12em]">
-              {title}
-            </span>
+            {iconExpanded ?? <span className="shrink-0 flex text-accent">{icon}</span>}
+            {onTitleClick ? (
+              <button
+                onClick={onTitleClick}
+                className="flex-1 min-w-0 truncate text-left text-sm font-bold uppercase tracking-[0.12em] transition hover:text-accent"
+              >
+                {title}
+              </button>
+            ) : (
+              <span className="flex-1 min-w-0 truncate text-sm font-bold uppercase tracking-[0.12em]">
+                {title}
+              </span>
+            )}
             {count > 0 && (
               <span
                 title={t("sidebar.activeCount", { count })}