chore(ui): 统一后台按钮样式 + 清理少量 inline margin

public/css/admin-base.css

@@ -92,6 +92,74 @@ input,select,button,textarea,
     box-sizing:border-box;
 }
 button{cursor:pointer;}
+
+/* Buttons (UI Components)
+ * 说明：统一总台/站点后台/商家后台按钮风格（四端后台美化第一步）。
+ */
+.btn,
+button.btn,
+.btn-secondary,
+button.btn-secondary,
+.btn-danger,
+button.btn-danger{
+    display:inline-flex;
+    align-items:center;
+    justify-content:center;
+    gap:6px;
+    padding:10px 14px;
+    border-radius:10px;
+    font-weight:600;
+    text-decoration:none;
+    border:1px solid transparent;
+    cursor:pointer;
+}
+
+.btn,
+button.btn{
+    background:#1d4ed8;
+    border-color:#1d4ed8;
+    color:#dbeafe;
+}
+.btn:hover,
+button.btn:hover{
+    background:#1e40af;
+    border-color:#1e40af;
+    text-decoration:none;
+}
+
+.btn-secondary,
+button.btn-secondary{
+    background:transparent;
+    border-color:#334155;
+    color:#cbd5e1;
+}
+.btn-secondary:hover,
+button.btn-secondary:hover{
+    background:#1e293b;
+    border-color:#475569;
+    text-decoration:none;
+}
+
+.btn-danger,
+button.btn-danger{
+    background:#7f1d1d;
+    border-color:#7f1d1d;
+    color:#fecaca;
+}
+.btn-danger:hover,
+button.btn-danger:hover{
+    background:#991b1b;
+    border-color:#991b1b;
+    text-decoration:none;
+}
+
+.btn-sm,
+button.btn-sm{
+    padding:8px 10px;
+    border-radius:9px;
+    font-size:13px;
+}
+
 textarea.w-full,input.w-full{width:100%;}
 input.w-140{width:140px;}
 input.w-90{width:90px;}