Expose PocketBase URL to client-side for OIDC auth

POCKETBASE_URL was only available server-side, causing the login page
to fall back to localhost:8090 in the browser. Renamed to
NEXT_PUBLIC_POCKETBASE_URL so Next.js bundles it into client code.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/pocketbase.ts

@@ -5,7 +5,8 @@ import PocketBase, { type RecordModel } from "pocketbase";
 
 import type { OverrideType, User } from "@/types";
 
-const POCKETBASE_URL = process.env.POCKETBASE_URL || "http://localhost:8090";
+const POCKETBASE_URL =
+  process.env.NEXT_PUBLIC_POCKETBASE_URL || "http://localhost:8090";
 
 /**
  * Singleton PocketBase client for client-side usage.