Refactor demo login as an authentication method

Use the authentication method system for the demo login and the
generated accounts.  This makes it possible to toggle it off on
production systems as these shouldn't have it enabled at all.

components/LogIn.vue

@@ -0,0 +1,29 @@
+<!--
+	SPDX-FileCopyrightText: © 2025 Hornwitser <code@hornwitser.no>
+	SPDX-License-Identifier: AGPL-3.0-or-later
+-->
+<template>
+	<div>
+		<LogInDemo v-if="authDemoEnabled" />
+		<LogInTelegram v-if="authTelegramEnabled" />
+		<template v-if="noAuth">No authentication method has been enabled in the configuration.</template>
+	</div>
+</template>
+
+<script lang="ts" setup>
+const runtimeConfig = useRuntimeConfig();
+const authDemoEnabled = runtimeConfig.public.authDemoEnabled;
+const authTelegramEnabled = runtimeConfig.public.authTelegramEnabled;
+const noAuth =
+	!authDemoEnabled
+	&& !authTelegramEnabled
+;
+</script>
+
+<style lang="css" scoped>
+div>* + *::before {
+	content: "\2013  or \2013 ";
+	display: block;
+	margin-block: 0.5rem;
+}
+</style>

components/LogInDemo.vue

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+<!--
+	SPDX-FileCopyrightText: © 2025 Hornwitser <code@hornwitser.no>
+	SPDX-License-Identifier: AGPL-3.0-or-later
+-->
+<template>
+	<form @submit.prevent="logIn">
+		<label>
+			Demo:
+			<input v-model="name" type="text" placeholder="Name" required>
+			<button type="submit">Log In</button>
+		</label>
+	</form>
+</template>
+
+<script lang="ts" setup>
+const sessionStore = useSessionStore();
+const route = useRoute();
+
+const name = ref("");
+async function logIn() {
+	try {
+		const session = await $fetch("/api/auth/ap/demo-login", {
+			method: "POST",
+			body: { name: name.value },
+		});
+		await sessionStore.update(session);
+		if (!session.account) {
+			await navigateTo("/register");
+		} else if (route.path === "/register") {
+			await navigateTo("/");
+		}
+
+	} catch (err: any) {
+		alert(err.data?.message ?? err.message);
+	}
+}
+</script>
+
+<style>
+
+</style>