update frontend with bulma css and home&404 pages

frontend/src/views/Home.vue

@@ -1,8 +1,20 @@
 <script setup lang="ts"></script>
 
 <template>
-  <h1>Congratulations</h1>
-  <p>This is home.</p>
+  <div class="container">
+    <article>
+      <h1 class="title">coconut-leaf</h1>
+      <p>A light, self-host and multi-account calendar system.</p>
+      <p>The original intention of this system is served for yyc12345 personal use.</p>
+      <br />
+      <p>See our <a href="https://github.com/yyc12345/coconut-leaf">GitHub project</a> for the source code in detail.</p>
+      <p>The source code of this project is licensed under <a href="https://www.gnu.org/licenses/agpl-3.0.html">AGPL v3</a>.</p>
+    </article>
+  </div>
 </template>
 
-<style scoped></style>
+<style scoped>
+div.container {
+  margin-top: 1.25rem;
+}
+</style>

frontend/src/views/NotFound.vue

@@ -0,0 +1,17 @@
+<script setup lang="ts"></script>
+
+<template>
+  <div class="container">
+    <article>
+      <h1 class="title">Oops!</h1>
+      <p>You are wandering in the desert of coconut-leaf.</p>
+      <p>Please back to previous page and try again.</p>
+    </article>
+  </div>
+</template>
+
+<style scoped>
+div.container {
+  margin-top: 1.25rem;
+}
+</style>

frontend/src/views/Page404.vue

@@ -1,8 +0,0 @@
-<script setup lang="ts"></script>
-
-<template>
-  <h1>Congratulations</h1>
-  <p>404 Not Found</p>
-</template>
-
-<style scoped></style>