chore: 编译器警告清理 — 22 条全部消除，workspace 零警告

erp-ai(8): 移除未用 import + serde 结构体 #[allow(dead_code)]
erp-plugin(5): 移除未用 import + FromQueryResult 结构体允许
erp-health(8): 移除未用 import/变量 + FromQueryResult 字段允许
erp-server(1): AnalyticsEvent.timestamp 允许（未来分析集成）

crates/erp-ai/src/service/auto_analysis.rs

@@ -5,8 +5,8 @@
 
 use std::time::Duration;
 
-use erp_core::health_provider::{HealthDataProvider, TimeRange};
-use sea_orm::{EntityTrait, FromQueryResult, Statement};
+use erp_core::health_provider::TimeRange;
+use sea_orm::{FromQueryResult, Statement};
 use uuid::Uuid;
 
 use crate::dto::AnalysisType;

crates/erp-ai/src/service/reanalysis.rs

@@ -11,6 +11,7 @@ pub async fn handle_reanalysis_requested(
     #[derive(Debug, FromQueryResult)]
     struct OriginalSuggestion {
         baseline_snapshot: Option<serde_json::Value>,
+        #[allow(dead_code)] // FromQueryResult 映射需要，当前未读取
         params: Option<serde_json::Value>,
         risk_level: Option<String>,
     }