feat: improve OIDC login flow and stores handling

src/OIDCCallback.svelte

@@ -0,0 +1,35 @@
+<script>
+	import { uploadID } from "$lib/services/lnv";
+	import { getOIDCUser } from "$lib/services/oidc";
+	import { onMount } from "svelte";
+
+	const url = new URL(location.href);
+	const code = url.searchParams.get("code");
+	const state = url.searchParams.get("state");
+	const storedState = localStorage.getItem("lnv-oidcstate");
+	const codeVerifier = localStorage.getItem("lnv-codeVerifier");
+	localStorage.removeItem("lnv-oidcstate");
+	localStorage.removeItem("lnv-codeVerifier");
+
+	async function login() {
+		if (!code || !state || !codeVerifier || !storedState) {
+			alert("Missing code, state, codeVerifier or storedState.");
+			return;
+		}
+		if (state !== storedState) {
+			alert("State mismatch. Please try again.");
+			return;
+		}
+	
+		const token = await getOIDCUser(code, codeVerifier);
+		localStorage.setItem("lnv-id", token.id_token);
+		localStorage.setItem("lnv-token", token.access_token);
+		localStorage.setItem("lnv-refresh", token.refresh_token);
+		await uploadID();
+	}
+
+	onMount(async () => {
+		await login();
+		location.href = "/";
+	})
+</script>