fix(timer): 完成页圆环覆盖弹窗 + 自定义确认 modal 替代 wx.showModal

训练完成的三个相关 bug:
1. progress-ring 圆环覆盖完成页弹窗 → @tap ring wx:if 让完成态时直接 unmount
2. 完成弹窗内按钮需要点 2 次才能响应 → completion-mask 加 catchtouchmove 拦截 touchmove
3. wx.showModal "结束训练" 系统弹窗在 stacking context 下 hit-test 不稳

根因: .timer-page.page-enter 永久保留 transform: translateY(0),
创建永久 stacking context,影响 native modal 的 WebView 部分 hit-test。

修法:
- 新增自定义 stop-confirm modal (catchtouchmove + 内部 catchtap + bindtap),
  与 ui-modal/settings.plan-editor-mask 同模式,行为可靠
- completion-mask 用相同模式拦截 touchmove
- 顺便修 overtime-badge 暗色 (rgba(var(--success-rgb)))

pages/timer/timer.wxss

@@ -70,8 +70,8 @@
   bottom: 10rpx;
   left: 50%;
   transform: translateX(-50%);
-  background: rgba(76, 175, 80, 0.12);
-  border: 2rpx solid rgba(76, 175, 80, 0.3);
+  background: rgba(var(--success-rgb), 0.12);
+  border: 2rpx solid rgba(var(--success-rgb), 0.3);
   color: var(--success);
   padding: 8rpx 24rpx;
   border-radius: 24rpx;
@@ -393,3 +393,84 @@
   font-size: 26rpx;
   margin-top: 4rpx;
 }
+
+/* ---- stop confirm modal (替代 wx.showModal,自定义实现) ---- */
+.stop-confirm-mask {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.55);
+  z-index: 9999;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 40rpx;
+  box-sizing: border-box;
+  animation: completionMaskIn 0.25s ease;
+}
+
+.stop-confirm-card {
+  width: 100%;
+  max-width: 560rpx;
+  background: var(--card-bg);
+  border-radius: 24rpx;
+  padding: 48rpx 40rpx 24rpx;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  box-shadow: 0 12rpx 36rpx rgba(0, 0, 0, 0.22);
+  animation: stopConfirmPop 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
+}
+
+@keyframes stopConfirmPop {
+  0%   { transform: scale(0.85); opacity: 0; }
+  100% { transform: scale(1);    opacity: 1; }
+}
+
+.stop-confirm-title {
+  font-size: 32rpx;
+  font-weight: 700;
+  color: var(--text);
+  margin-bottom: 20rpx;
+  line-height: 1.3;
+}
+
+.stop-confirm-content {
+  font-size: 28rpx;
+  color: var(--text-secondary);
+  line-height: 1.5;
+  text-align: center;
+  margin-bottom: 40rpx;
+}
+
+.stop-confirm-actions {
+  display: flex;
+  width: 100%;
+  gap: 16rpx;
+  border-top: 1rpx solid var(--border);
+  padding-top: 24rpx;
+}
+
+.stop-confirm-btn {
+  flex: 1;
+  height: 80rpx;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 30rpx;
+  font-weight: 600;
+  border-radius: 12rpx;
+  background: var(--bg-soft);
+  color: var(--text);
+  transition: transform 0.15s ease, opacity 0.15s ease, background 0.2s ease;
+}
+
+.stop-confirm-btn:active {
+  transform: scale(0.96);
+  opacity: 0.85;
+}
+
+.stop-confirm-btn--primary {
+  background: linear-gradient(135deg, var(--primary), var(--primary-light));
+  color: #FFFFFF;
+  box-shadow: 0 6rpx 16rpx rgba(var(--primary-rgb), 0.3);
+}