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/main.tsx

@@ -6,6 +6,7 @@ import ErrorBoundary from "./components/ErrorBoundary";
 import { ConfirmProvider } from "./components/ConfirmProvider";
 import { NavigationProvider } from "./components/NavigationProvider";
 import { FeedFiltersProvider } from "./components/FeedFiltersProvider";
+import { SavedViewsProvider } from "./components/SavedViewsProvider";
 import { PlaylistsProvider } from "./components/PlaylistsProvider";
 import { PlexProvider } from "./components/PlexProvider";
 import { ChannelsProvider } from "./components/ChannelsProvider";
@@ -57,19 +58,21 @@ const root =
           <ConfirmProvider>
             <NavigationProvider>
               <FeedFiltersProvider>
-                <PlaylistsProvider>
-                  <PlexProvider>
-                    <ChannelsProvider>
-                      <FeedViewProvider>
-                        <PrefsProvider>
-                          <WizardProvider>
-                            <App />
-                          </WizardProvider>
-                        </PrefsProvider>
-                      </FeedViewProvider>
-                    </ChannelsProvider>
-                  </PlexProvider>
-                </PlaylistsProvider>
+                <SavedViewsProvider>
+                  <PlaylistsProvider>
+                    <PlexProvider>
+                      <ChannelsProvider>
+                        <FeedViewProvider>
+                          <PrefsProvider>
+                            <WizardProvider>
+                              <App />
+                            </WizardProvider>
+                          </PrefsProvider>
+                        </FeedViewProvider>
+                      </ChannelsProvider>
+                    </PlexProvider>
+                  </PlaylistsProvider>
+                </SavedViewsProvider>
               </FeedFiltersProvider>
             </NavigationProvider>
           </ConfirmProvider>