chore: batch commit remaining changes

Includes search engine improvements, Alembic migrations,
new services (pubmed_daily_update, query_expansion),
frontend updates, and documentation sync.

frontend/src/composables/useDisplaySettings.ts

@@ -0,0 +1,46 @@
+import { reactive, watch } from 'vue'
+import type { DisplaySettings } from '../types'
+
+const STORAGE_KEY = 'search:displaySettings'
+
+const defaults: DisplaySettings = {
+  showAuthors: true,
+  showAffiliation: true,
+  showJournal: true,
+  showPmid: true,
+  showDoi: true,
+  showAbstract: true,
+  showStudyTypes: true,
+  showTags: true,
+  showCitedBy: true,
+  showAiSummary: true,
+  showActions: true,
+  showBadges: true,
+  showSummary: true,
+  showPubmed: true,
+}
+
+function loadSettings(): DisplaySettings {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY)
+    if (raw) {
+      const parsed = JSON.parse(raw)
+      return { ...defaults, ...parsed }
+    }
+  } catch { /* ignore */ }
+  return { ...defaults }
+}
+
+const settings = reactive<DisplaySettings>(loadSettings())
+
+watch(
+  () => ({ ...settings }),
+  (val) => {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(val))
+  },
+  { deep: true },
+)
+
+export function useDisplaySettings() {
+  return settings
+}