M6 1902b: facet bar + saved views UI (frontend)

The dead-simple facet bar over the board + saved views in the sidebar,
completing task 1902. Filter state lives in the URL query, so a filtered
board is a shareable lens and a saved view is just a link ("one space,
many lenses").

- notes/facets.ts: facetsFromQuery / facetsToQuery / facetCount helpers.
- FilterBar.vue (board only): a "Filters (N)" toggle expanding to text
  search + color swatches + label chips + has-reminder / has-attachment /
  Lists / Notes toggles + a created-date range; Clear + "Save view".
  Each control writes the URL query (router.replace).
- notes store: load(view, label, facets) builds the query; NoteFacets type
  + activeFacets; import reload preserves active facets.
- savedFilters store + sidebar "Views" section (each a query-link, delete
  on hover); loaded on mount.
- BoardView derives facets from the query, reloads on facet change (ignores
  ?open=), and shows a "no notes match these filters" empty state.
- Backend: saved-filter param whitelist keys on `label` (matches the
  repeatable ?label= query) so saved views keep their labels. New filter
  icon.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/AppShell.vue

@@ -4,11 +4,13 @@ import { useRoute, useRouter } from "vue-router";
 import { useSessionStore } from "../stores/session";
 import { useConfigStore } from "../stores/config";
 import { useLabelsStore } from "../stores/labels";
+import { useSavedFiltersStore, type SavedFilter } from "../stores/savedFilters";
 import { useUiStore } from "../stores/ui";
 import CommandPalette from "./CommandPalette.vue";
 import Icon from "./Icon.vue";
 import ImportNotes from "./ImportNotes.vue";
 import LabelsModal from "./LabelsModal.vue";
+import { facetsToQuery } from "../notes/facets";
 import { NOTE_SWATCH_CLASSES, type NoteColor } from "../notes/colors";
 
 const route = useRoute();
@@ -16,8 +18,18 @@ const router = useRouter();
 const session = useSessionStore();
 const config = useConfigStore();
 const labels = useLabelsStore();
+const savedFilters = useSavedFiltersStore();
 const ui = useUiStore();
 
+async function removeView(f: SavedFilter) {
+  if (!window.confirm(`Delete the "${f.name}" view?`)) return;
+  try {
+    await savedFilters.remove(f.id);
+  } catch {
+    ui.showToast("Couldn't delete that view.");
+  }
+}
+
 const managing = ref(false);
 const showShortcuts = ref(false);
 const paletteOpen = ref(false);
@@ -140,6 +152,7 @@ function onKeydown(e: KeyboardEvent) {
 
 onMounted(() => {
   if (!labels.loaded) void labels.load();
+  if (!savedFilters.loaded) void savedFilters.load();
   window.addEventListener("keydown", onKeydown);
 });
 onBeforeUnmount(() => window.removeEventListener("keydown", onKeydown));
@@ -289,6 +302,29 @@ async function signOut() {
             <span class="truncate">{{ lb.name }}</span>
           </RouterLink>
 
+          <template v-if="savedFilters.items.length">
+            <div class="mt-3 px-3 pb-1">
+              <span class="text-xs font-semibold uppercase tracking-wide text-neutral-400">Views</span>
+            </div>
+            <RouterLink
+              v-for="f in savedFilters.items"
+              :key="f.id"
+              :to="{ path: '/', query: facetsToQuery(f.params) }"
+              class="nav-link group/view"
+            >
+              <Icon name="filter" />
+              <span class="flex-1 truncate">{{ f.name }}</span>
+              <button
+                type="button"
+                class="text-neutral-400 opacity-0 hover:text-red-500 group-hover/view:opacity-100"
+                :aria-label="`Delete view ${f.name}`"
+                @click.prevent.stop="removeView(f)"
+              >
+                ×
+              </button>
+            </RouterLink>
+          </template>
+
           <RouterLink to="/archive" class="nav-link mt-3" :class="route.name === 'archive' ? 'nav-link-active' : ''">
             <Icon name="archive" /> Archive
           </RouterLink>