style(login): 优化按钮文本样式和成功状态背景

更新按钮文本颜色、字重和字间距，添加文本阴影和呼吸动画。修改成功状态的背景渐变和阴影效果。

assets/css/mine/login.scss

@@ -271,7 +271,23 @@
             }
 
             .btn-text {
-                letter-spacing: 4rpx;
+                color: #ffffff;
+                font-weight: 500;
+                letter-spacing: 2rpx;
+                text-shadow: 0 1rpx 2rpx rgba(13, 71, 161, 0.45);
+                animation: textBreath 1.6s ease-in-out infinite;
+            }
+        }
+
+        @keyframes textBreath {
+
+            0%,
+            100% {
+                opacity: 0.85;
+            }
+
+            50% {
+                opacity: 1;
             }
         }
 
@@ -289,7 +305,8 @@
 
         &.success {
             .btn-bg {
-                background: linear-gradient(135deg, #10b981 0%, #059669 100%);
+                background: linear-gradient(135deg, #3b82f6 0%, #1969f9 100%);
+                box-shadow: 0 4rpx 16rpx rgba(25, 105, 249, 0.3);
                 animation: successPop 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
             }