fix(growth,memory,hands): 穷尽审计后 4 项修复 — 伪造时间戳+测试覆盖+注释纠正

CRITICAL:
- user_profile_store: find_active_pains_since 改为 find_active_pains，
  移除无意义 .filter(|_| true)，不再伪造 created_at=since

HIGH:
- daily_report: 移除虚假的 "Emits Tauri event" 注释（事件发射是调用方职责）
- daily_report: chrono::Local → chrono::Utc 一致性修复
- 新增 8 个单元测试: PainPoint 系列测试 + find_since + get_events_since

验证: zclaw-memory 54 PASS, zclaw-growth 151 PASS, zclaw-hands 5 PASS

crates/zclaw-growth/src/experience_store.rs

@@ -457,4 +457,26 @@ mod tests {
         // Content should reflect the latest version.
         assert_eq!(found[0].context, "context v3");
     }
+
+    #[tokio::test]
+    async fn test_find_since_filters_by_date() {
+        let viking = Arc::new(VikingAdapter::in_memory());
+        let store = ExperienceStore::new(viking);
+
+        let exp = Experience::new(
+            "agent-1", "recent pattern", "ctx",
+            vec!["step".into()], "ok",
+        );
+        store.store_experience(&exp).await.unwrap();
+
+        // Query with since=far past → should find it
+        let old_since = Utc::now() - chrono::Duration::days(365);
+        let found = store.find_since("agent-1", old_since).await.unwrap();
+        assert_eq!(found.len(), 1);
+
+        // Query with since=far future → should not find it
+        let future_since = Utc::now() + chrono::Duration::days(365);
+        let found = store.find_since("agent-1", future_since).await.unwrap();
+        assert!(found.is_empty());
+    }
 }