feat: 任务详情页语音播报功能 (REQ-20260508-0006)

- 详情页右侧悬浮播放按钮（36dp半透明圆形）
- 播报内容：任务名+地点+时间+积分(>0)+备注，空字段跳过
- 播放中按钮高亮+图标切换，再点停止
- 离开页面自动停止播放
- TTS播放期间抑制提示音，避免叠加

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/res/drawable/ic_speaker_stop.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- 停止图标（语音播报停止状态）24×24dp -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <!-- 喇叭主体 -->
+    <path
+        android:fillColor="@color/text_primary"
+        android:pathData="M3,9v6h4l5,5V4L7,9H3z" />
+    <!-- 叉号（静音标记） -->
+    <path
+        android:fillColor="@color/text_primary"
+        android:pathData="M16.5,12c0,-1.77 -1.02,-3.29 -2.5,-4.03v2.21l2.45,2.45c0.03,-0.2 0.05,-0.41 0.05,-0.63z" />
+    <path
+        android:fillColor="@color/text_primary"
+        android:pathData="M19,12c0,0.94 -0.2,1.82 -0.54,2.64l1.51,1.51C20.63,14.91 21,13.5 21,12c0,-4.28 -2.99,-7.86 -7,-8.77v2.06c2.89,0.86 5,3.54 5,6.71z" />
+    <path
+        android:fillColor="@color/text_primary"
+        android:pathData="M4.27,3L3,4.27 7.73,9H3v6h4l5,5v-6.73l4.25,4.25c-0.67,0.52 -1.42,0.93 -2.25,1.18v2.06c1.38,-0.31 2.63,-0.95 3.69,-1.81L19.73,21 21,19.73l-9,-9L4.27,3z" />
+</vector>