feat: tag all PocketBase fetches for ISR cache invalidation

Each getCollection/getFirstRecord call now passes the collection name
as a cache tag so revalidateTag can target individual collections.

app/[[...slug]]/page.tsx

@@ -10,6 +10,7 @@ import { SectionsAccordion } from '$widgets/SectionsAccordion';
 export async function generateStaticParams() {
   const { items: sections } = await getCollection<SectionRecord>('sections', {
     sort: 'order',
+    tags: ['sections'],
   });
   return [{}, ...sections.map((s) => ({ slug: [s.slug] }))];
 }
@@ -26,6 +27,7 @@ export default async function SectionPage({ params }: Props) {
 
   const { items: sections } = await getCollection<SectionRecord>('sections', {
     sort: 'order',
+    tags: ['sections'],
   });
 
   if (sections.length === 0) {