Complete bootstrap base frontend prototype.

- login page and playlist setting page frontend templates.
- fast API route.
- reading and saving config files
- mock login logic for UI interaction demo

app/templates/login.html

@@ -0,0 +1,37 @@
+{% extends "base.html" %}
+
+{% block title %}登录信息{% endblock %}
+
+{% block content %}
+<h2>🔐 登录信息</h2>
+<form method="post" action="/login">
+    <div class="mb-3">
+        <label for="user" class="form-label">用户名</label>
+        <input type="text" class="form-control" id="user" name="user">
+    </div>
+    <div class="mb-3">
+        <label for="pw" class="form-label">密码</label>
+        <input type="password" class="form-control" id="pw" name="pw">
+    </div>
+    <div class="mb-3">
+        <label for="url" class="form-label">服务器地址</label>
+        <input type="text" class="form-control" id="url" name="url" placeholder="127.0.0.1">
+    </div>
+    <div class="mb-3">
+        <label for="port" class="form-label">端口</label>
+        <input type="text" class="form-control" id="port" name="port" placeholder="32400">
+    </div>
+    <div class="mb-3">
+        <label for="library" class="form-label">选择库</label>
+        <select class="form-select" id="library" name="library">
+            <option>Music</option>
+            <option>Podcast</option>
+        </select>
+    </div>
+    <button type="submit" class="btn btn-primary">连接</button>
+</form>
+
+{% if message %}
+<div class="alert alert-{{ 'success' if success else 'danger' }} mt-4">{{ message }}</div>
+{% endif %}
+{% endblock %}