feat: centralized Notion-style taxonomy management in settings

Single persistent option pool per taxonomy (7 fields: offer
categoria/ticket/tipo/obiettivo + catalog fase/offerta/pacchetto),
stored as JSON in the settings table (no DB migration).

- src/lib/taxonomy.ts: pools with lazy seed from in-use values,
  add/remove(cascade)/rename helpers
- Inline creation anywhere registers into the pool (save offer,
  addServiceOption, updateServiceField fase, quickAdd, create macro)
- Deselecting on a row never touches the pool; global delete only
  from settings (cascade-strips tags / nulls columns)
- getOfferFieldOptions + getCatalogFieldOptions read from pools
- Settings: TaxonomyManager (offer + catalog groups), confirm on delete

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/admin/impostazioni/actions.ts

@@ -1,33 +1,42 @@
 "use server";
 
-import { getJsonPool, updateJsonPool, SETTINGS_KEYS } from "@/lib/settings";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
 import { revalidatePath } from "next/cache";
+import {
+  addPoolValue,
+  removePoolValue,
+  TAXONOMY_FIELDS,
+  type TaxonomyFieldId,
+} from "@/lib/taxonomy";
 
-type PoolName = "tipo" | "obiettivo" | "categoria";
-
-function poolKey(pool: PoolName): string {
-  switch (pool) {
-    case "tipo":      return SETTINGS_KEYS.OFFER_TIPO_POOL;
-    case "obiettivo": return SETTINGS_KEYS.OFFER_OBIETTIVO_POOL;
-    case "categoria": return SETTINGS_KEYS.OFFER_CATEGORIA_POOL;
-  }
+async function requireAdmin() {
+  const session = await getServerSession(authOptions);
+  if (!session) throw new Error("Non autorizzato");
 }
 
-export async function addPoolValue(pool: PoolName, value: string): Promise<void> {
-  const trimmed = value.trim();
-  if (!trimmed) return;
-  const key = poolKey(pool);
-  const current = await getJsonPool(key);
-  if (current.includes(trimmed)) return;
-  await updateJsonPool(key, [...current, trimmed]);
+function assertField(fieldId: string): asserts fieldId is TaxonomyFieldId {
+  if (!(fieldId in TAXONOMY_FIELDS)) throw new Error(`Tassonomia non valida: ${fieldId}`);
+}
+
+function revalidateAll() {
   revalidatePath("/admin/impostazioni");
   revalidatePath("/admin/offers");
+  revalidatePath("/admin/catalog");
 }
 
-export async function removePoolValue(pool: PoolName, value: string): Promise<void> {
-  const key = poolKey(pool);
-  const current = await getJsonPool(key);
-  await updateJsonPool(key, current.filter((v) => v !== value));
-  revalidatePath("/admin/impostazioni");
-  revalidatePath("/admin/offers");
+export async function addTaxonomyValue(fieldId: string, value: string): Promise<void> {
+  await requireAdmin();
+  assertField(fieldId);
+  await addPoolValue(fieldId, value);
+  revalidateAll();
+}
+
+// Global delete: removes the value from the pool AND cascade-strips it from every
+// offer/service using it.
+export async function removeTaxonomyValue(fieldId: string, value: string): Promise<void> {
+  await requireAdmin();
+  assertField(fieldId);
+  await removePoolValue(fieldId, value);
+  revalidateAll();
 }