fix: db.get_or_404 -> query.get_or_404 + rename to Palladium Monitor

- 修复删除快照时 AttributeError: SQLAlchemy.get_or_404 (低版本兼容)
- UI/标题/邮件主题从 'Palladium Z1 Monitor' 改为 'Palladium Monitor'

templates/email_config.html

@@ -1,5 +1,5 @@
 {% extends "base.html" %}
-{% block title %}邮件配置 — Palladium Z1 Monitor{% endblock %}
+{% block title %}邮件配置 — Palladium Monitor{% endblock %}
 
 {% block content %}
 
@@ -81,7 +81,7 @@
             </div>
             <div class="form-group">
                 <label for="cfg_from_name">发件人名称</label>
-                <input type="text" id="cfg_from_name" placeholder="Palladium Z1 Monitor">
+                <input type="text" id="cfg_from_name" placeholder="Palladium Monitor">
             </div>
         </div>