feat: implement initial user authentication, session management, and admin dashboard routing with

templates/login.html

@@ -0,0 +1,17 @@
+{% extends "base.html" %}
+{% block title %}Dungeon Login{% endblock %}
+{% block content %}
+<div class="card">
+    <h2>Enter the Dungeon</h2>
+    {% if let Some(err) = error %}
+    <div class="error">{{ err }}</div>
+    {% endif %}
+    <form method="POST" action="/__dungeon/login">
+        <label>Username</label>
+        <input type="text" name="username" required autocomplete="username">
+        <label>Password</label>
+        <input type="password" name="password" required autocomplete="current-password">
+        <button type="submit">Login</button>
+    </form>
+</div>
+{% endblock %}