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/playlist.html

@@ -0,0 +1,26 @@
+{% extends "base.html" %}
+
+{% block title %}播放列表设置{% endblock %}
+
+{% block content %}
+<h2>📂 播放列表设置</h2>
+<form method="post" action="/playlist">
+    <div class="mb-3">
+        <label for="address" class="form-label">播放列表地址</label>
+        <input type="text" class="form-control" id="address" name="address">
+    </div>
+    <div class="mb-3">
+        <label for="interval" class="form-label">同步时间间隔</label>
+        <select class="form-select" id="interval" name="interval">
+            <option value="5">每 5 分钟</option>
+            <option value="10">每 10 分钟</option>
+            <option value="30">每 30 分钟</option>
+        </select>
+    </div>
+    <button type="submit" class="btn btn-success">保存设置</button>
+</form>
+
+{% if message %}
+<div class="alert alert-info mt-4">{{ message }}</div>
+{% endif %}
+{% endblock %}