Fix redirect loop by setting NEXT_PUBLIC_ENTE_ALBUMS_ENDPOINT

The app was redirecting to /shared-albums because albumsAppOrigin()
returned the same host as the current URL after runtime replacement.
By setting NEXT_PUBLIC_ENTE_ALBUMS_ENDPOINT at build time to a
placeholder and replacing it at runtime with the full path-based URL,
the host comparison will fail and prevent the redirect loop.

Version bump to 0.3.1

CloudronManifest.json

@@ -7,7 +7,7 @@
   "contactEmail": "contact@ente.io",
   "website": "https://ente.io",
   "tagline": "Open source, end-to-end encrypted photo backup",
-  "version": "0.3.0",
+  "version": "0.3.1",
   "upstreamVersion": "git-main",
   "healthCheckPath": "/health",
   "httpPort": 3080,