feat: add tags/revalidate options to PocketBase fetch client

PB_URL falls back through PB_URL → NEXT_PUBLIC_PB_URL → localhost so
internal Docker hostname is used server-side without leaking into the
client bundle. cache: force-cache replaced with next: { tags, revalidate }
for ISR tag-based invalidation.

src/shared/api/client.ts

@@ -4,13 +4,10 @@ import type { ListResponse } from './types';
  * Native fetch wrapper for PocketBase API requests.
  */
 
-const PB_URL =
-  process.env.NEXT_PUBLIC_PB_URL ||
-  (process.env.NODE_ENV === 'production'
-    ? (() => {
-        throw new Error('NEXT_PUBLIC_PB_URL is not set');
-      })()
-    : 'http://127.0.0.1:8090');
+/* Prefer the server-only var (not exposed to the browser bundle),
+ * fall back to the public var for client-side usage, then to the
+ * local dev default. */
+const PB_URL = process.env.PB_URL ?? process.env.NEXT_PUBLIC_PB_URL ?? 'http://127.0.0.1:8090';
 
 /**
  * Options for PocketBase collection fetching.
@@ -28,13 +25,23 @@ export type PBFetchOptions = {
    * Fields to expand (e.g., "stack")
    */
   expand?: string;
+  /**
+   * Cache tags for on-demand revalidation via `revalidateTag`.
+   * Typically set to the collection name.
+   */
+  tags?: string[];
+  /**
+   * ISR revalidation interval in seconds.
+   * @default 3600
+   */
+  revalidate?: number;
 };
 
 /**
  * Fetch a list of records from a PocketBase collection.
  */
 export async function getCollection<T>(collection: string, options: PBFetchOptions = {}): Promise<ListResponse<T>> {
-  const { sort, filter, expand } = options;
+  const { sort, filter, expand, tags, revalidate } = options;
 
   const params = new URLSearchParams();
   if (sort) {
@@ -49,9 +56,12 @@ export async function getCollection<T>(collection: string, options: PBFetchOptio
 
   const url = `${PB_URL}/api/collections/${collection}/records?${params.toString()}`;
 
-  /* force-cache deduplicates identical fetches during the static build phase;
-   * it has no runtime effect in `output: 'export'` mode. */
-  const res = await fetch(url, { cache: 'force-cache' });
+  const res = await fetch(url, {
+    next: {
+      tags: tags ?? [],
+      revalidate: revalidate ?? 3600,
+    },
+  });
 
   if (!res.ok) {
     throw new Error(`PocketBase ${res.status} ${res.statusText} on collection "${collection}"`);