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-hands/src/hands/daily_report.rs

@@ -5,9 +5,12 @@
 //!   1. Yesterday's conversation summary
 //!   2. Unresolved pain points follow-up
 //!   3. Recent experience highlights
-//!   4. Industry news placeholder
+//!   4. Industry-specific daily reminder
 //!
-//! Emits `daily-report:ready` Tauri event and persists to VikingStorage.
+//! The caller (SchedulerService or Tauri command) is responsible for:
+//!   - Assembling input data (trajectory summary, pain points, experiences)
+//!   - Emitting `daily-report:ready` Tauri event after execution
+//!   - Persisting the report to VikingStorage
 
 use async_trait::async_trait;
 use serde_json::Value;
@@ -119,7 +122,7 @@ impl DailyReportHand {
             _ => "综合",
         };
 
-        let date = chrono::Local::now().format("%Y年%m月%d日").to_string();
+        let date = chrono::Utc::now().format("%Y年%m月%d日").to_string();
 
         let mut sections = vec![
             format!("# {} 管家日报 — {}", industry_label, date),