feat(scholars): add multiselect and bulk actions (delete, toggle, export)

Add Set<number>-based selection state to ScholarsPage with checkboxes
in both table and card views, select-all toggle, and stale-key pruning.

Backend: POST /scholars/bulk-delete, POST /scholars/bulk-toggle, and
GET /scholars/export?ids= filter. Service functions use user-scoped
queries. Structured logging for bulk operations.

Frontend: useScholarBulkActions composable extracts selection and bulk
action logic. AppSelect-based action dropdown with dynamic options.
Delete prompts window.confirm; enable/disable applies immediately.
Export downloads filtered JSON.

Includes integration tests for all bulk endpoints and frontend unit
tests for selection toggle, select-all, and stale pruning.

frontend/src/features/scholars/composables/useScholarBulkActions.ts

@@ -0,0 +1,195 @@
+import { computed, ref, watch, type Ref } from "vue";
+
+import {
+  bulkDeleteScholars,
+  bulkToggleScholars,
+  exportScholarData,
+  type ScholarProfile,
+} from "@/features/scholars";
+import { ApiRequestError } from "@/lib/api/errors";
+
+export type ScholarBulkAction =
+  | "delete_selected"
+  | "enable_selected"
+  | "disable_selected"
+  | "export_selected"
+  | "clear_selection"
+  | "select_all";
+
+export interface ScholarBulkActionOption {
+  value: ScholarBulkAction;
+  label: string;
+}
+
+export interface BulkActionCallbacks {
+  clearMessages: () => void;
+  assignError: (error: unknown, fallback: string) => void;
+  setSuccess: (msg: string) => void;
+  reloadScholars: () => Promise<void>;
+}
+
+export function useScholarBulkActions(
+  visibleScholars: Ref<ScholarProfile[]>,
+  callbacks: BulkActionCallbacks,
+) {
+  const selectedIds = ref<Set<number>>(new Set());
+  const bulkAction = ref<ScholarBulkAction>("select_all");
+  const bulkBusy = ref(false);
+
+  const selectedCount = computed(() => selectedIds.value.size);
+  const hasSelection = computed(() => selectedCount.value > 0);
+
+  const allVisibleSelected = computed(() => {
+    if (visibleScholars.value.length === 0) return false;
+    for (const item of visibleScholars.value) {
+      if (!selectedIds.value.has(item.id)) return false;
+    }
+    return true;
+  });
+
+  const bulkActionOptions = computed<ScholarBulkActionOption[]>(() => {
+    if (!hasSelection.value) return [{ value: "select_all", label: "Select all" }];
+    const n = selectedCount.value;
+    return [
+      { value: "delete_selected", label: `Delete selected (${n})` },
+      { value: "enable_selected", label: `Enable selected (${n})` },
+      { value: "disable_selected", label: `Disable selected (${n})` },
+      { value: "export_selected", label: `Export selected (${n})` },
+      { value: "clear_selection", label: "Clear selection" },
+    ];
+  });
+
+  const bulkApplyLabel = computed(() => {
+    if (bulkBusy.value) return "Applying...";
+    if (bulkAction.value === "select_all") return "Select";
+    if (bulkAction.value === "clear_selection") return "Clear";
+    return "Apply";
+  });
+
+  const bulkApplyDisabled = computed(() => {
+    if (bulkBusy.value) return true;
+    if (bulkAction.value === "select_all") return visibleScholars.value.length === 0;
+    return selectedCount.value === 0;
+  });
+
+  // Prune stale selections when visible list changes
+  watch(visibleScholars, (items) => {
+    const validIds = new Set(items.map((item) => item.id));
+    const next = new Set<number>();
+    for (const id of selectedIds.value) {
+      if (validIds.has(id)) next.add(id);
+    }
+    if (next.size !== selectedIds.value.size) selectedIds.value = next;
+  });
+
+  // Reset bulk action dropdown when selection state changes
+  watch(hasSelection, (has) => {
+    const validValues = new Set(bulkActionOptions.value.map((o) => o.value));
+    if (validValues.has(bulkAction.value)) return;
+    bulkAction.value = has ? "delete_selected" : "select_all";
+  });
+
+  function onToggleAll(event: Event): void {
+    const checked = (event.target as HTMLInputElement).checked;
+    const next = new Set(selectedIds.value);
+    for (const item of visibleScholars.value) {
+      if (checked) { next.add(item.id); } else { next.delete(item.id); }
+    }
+    selectedIds.value = next;
+  }
+
+  function onToggleRow(id: number, event: Event): void {
+    const checked = (event.target as HTMLInputElement).checked;
+    const next = new Set(selectedIds.value);
+    if (checked) { next.add(id); } else { next.delete(id); }
+    selectedIds.value = next;
+  }
+
+  function downloadJsonFile(filename: string, payload: unknown): void {
+    const blob = new Blob([JSON.stringify(payload, null, 2)], { type: "application/json" });
+    const url = URL.createObjectURL(blob);
+    const anchor = document.createElement("a");
+    anchor.href = url;
+    anchor.download = filename;
+    anchor.click();
+    URL.revokeObjectURL(url);
+  }
+
+  async function onApplyBulkAction(): Promise<void> {
+    if (bulkApplyDisabled.value) return;
+    if (bulkAction.value === "select_all") {
+      selectedIds.value = new Set(visibleScholars.value.map((item) => item.id));
+      return;
+    }
+    if (bulkAction.value === "clear_selection") { selectedIds.value = new Set(); return; }
+    if (bulkAction.value === "delete_selected") { await onBulkDelete(); return; }
+    if (bulkAction.value === "enable_selected") { await onBulkToggle(true); return; }
+    if (bulkAction.value === "disable_selected") { await onBulkToggle(false); return; }
+    if (bulkAction.value === "export_selected") { await onBulkExport(); return; }
+  }
+
+  async function onBulkDelete(): Promise<void> {
+    const ids = [...selectedIds.value];
+    if (!window.confirm(`Delete ${ids.length} scholar(s)? This removes all linked publications and queue data.`)) return;
+    bulkBusy.value = true;
+    callbacks.clearMessages();
+    try {
+      const result = await bulkDeleteScholars(ids);
+      callbacks.setSuccess(`${result.deleted_count} scholar(s) deleted.`);
+      selectedIds.value = new Set();
+      await callbacks.reloadScholars();
+    } catch (error) {
+      callbacks.assignError(error, "Unable to bulk delete scholars.");
+    } finally {
+      bulkBusy.value = false;
+    }
+  }
+
+  async function onBulkToggle(isEnabled: boolean): Promise<void> {
+    bulkBusy.value = true;
+    callbacks.clearMessages();
+    try {
+      const ids = [...selectedIds.value];
+      const result = await bulkToggleScholars(ids, isEnabled);
+      const verb = isEnabled ? "enabled" : "disabled";
+      callbacks.setSuccess(`${result.updated_count} scholar(s) ${verb}.`);
+      selectedIds.value = new Set();
+      await callbacks.reloadScholars();
+    } catch (error) {
+      callbacks.assignError(error, `Unable to bulk ${isEnabled ? "enable" : "disable"} scholars.`);
+    } finally {
+      bulkBusy.value = false;
+    }
+  }
+
+  async function onBulkExport(): Promise<void> {
+    bulkBusy.value = true;
+    callbacks.clearMessages();
+    try {
+      const ids = [...selectedIds.value];
+      const payload = await exportScholarData(ids);
+      const dateSlug = payload.exported_at.slice(0, 10) || "unknown-date";
+      downloadJsonFile(`scholarr-export-${dateSlug}.json`, payload);
+      callbacks.setSuccess("Export complete.");
+    } catch (error) {
+      callbacks.assignError(error, "Unable to export selected scholars.");
+    } finally {
+      bulkBusy.value = false;
+    }
+  }
+
+  return {
+    selectedIds,
+    selectedCount,
+    hasSelection,
+    allVisibleSelected,
+    bulkAction,
+    bulkBusy,
+    bulkActionOptions,
+    bulkApplyLabel,
+    bulkApplyDisabled,
+    onToggleAll,
+    onToggleRow,
+    onApplyBulkAction,
+  };
+}