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/SavedViewsPopover.tsx

@@ -0,0 +1,84 @@
+import { useState, type ReactNode } from "react";
+import { useTranslation } from "react-i18next";
+import { Bookmark, Check, Settings2 } from "lucide-react";
+import { PopoverItem, PopoverSurface, useAnchoredPopover } from "./AnchoredPopover";
+import { useSavedViews } from "./SavedViewsProvider";
+
+// The saved-views quick-picker. The filter-panel header's icon (and the toolbar's view chip) use it as
+// their trigger: click → a popover list of the user's saved views (apply on click, the active one
+// checked) + a "Manage views…" entry that opens the Personal Views modal, where the editing lives.
+export default function SavedViewsPopover({
+  trigger,
+  className,
+  ariaLabel,
+  placement = "bottom-start",
+}: {
+  trigger: ReactNode;
+  className?: string;
+  ariaLabel?: string;
+  placement?: "bottom-start" | "bottom-end";
+}) {
+  const { t } = useTranslation();
+  const { views, activeViewId, apply, openModal } = useSavedViews();
+  const [open, setOpen] = useState(false);
+  const pop = useAnchoredPopover({ open, onOpenChange: setOpen, placement });
+  const label = ariaLabel ?? t("views.saved");
+  return (
+    <>
+      <button
+        type="button"
+        ref={pop.refs.setReference}
+        {...pop.getReferenceProps()}
+        aria-label={label}
+        className={className ?? "shrink-0 flex text-accent transition hover:text-fg"}
+      >
+        {trigger}
+      </button>
+      <PopoverSurface
+        popover={pop}
+        ariaLabel={label}
+        className="glass-menu min-w-56 rounded-xl p-1.5 shadow-lg animate-[popIn_0.16s_ease]"
+      >
+        {views.length === 0 ? (
+          <p className="px-2 py-1.5 text-2xs leading-snug text-muted">{t("views.empty")}</p>
+        ) : (
+          <div role="group" aria-label={label}>
+            {views.map((v) => (
+              <PopoverItem
+                key={v.id}
+                role="menuitemradio"
+                checked={v.id === activeViewId}
+                onSelect={() => {
+                  apply(v);
+                  setOpen(false);
+                }}
+                label={v.name}
+                className={`flex w-full items-center gap-2 rounded-md px-2 py-1.5 text-left text-sm transition ${
+                  v.id === activeViewId ? "text-fg" : "text-muted"
+                }`}
+              >
+                <Bookmark className="h-3.5 w-3.5 shrink-0 text-muted" aria-hidden="true" />
+                <span className="flex-1 truncate">{v.name}</span>
+                {v.id === activeViewId && <Check className="h-3.5 w-3.5 shrink-0 text-accent" />}
+              </PopoverItem>
+            ))}
+          </div>
+        )}
+        <div className="mt-1 border-t border-border pt-1">
+          <PopoverItem
+            role="menuitem"
+            onSelect={() => {
+              openModal();
+              setOpen(false);
+            }}
+            label={t("views.manage")}
+            className="flex w-full items-center gap-2 rounded-md px-2 py-1.5 text-left text-sm text-muted transition hover:text-fg"
+          >
+            <Settings2 className="h-3.5 w-3.5 shrink-0" aria-hidden="true" />
+            <span className="flex-1">{t("views.manage")}</span>
+          </PopoverItem>
+        </div>
+      </PopoverSurface>
+    </>
+  );
+}