feat(server-go): 区域发病统计（#22，rooms.region + region-stats）

server-go/internal/handler/trace.go

@@ -3,6 +3,7 @@ package handler
 import (
 	"encoding/json"
 	"net/http"
+	"strconv"
 	"time"
 
 	"silk-server-go/internal/middleware"
@@ -18,6 +19,7 @@ func RegisterTraceRoutes(rg *gin.RouterGroup, db *gorm.DB) {
 	read := middleware.RequirePermission(db, "trace:read")
 	write := middleware.RequirePermission(db, "trace:write")
 	rg.GET("/trace-records", read, listTraceRecords(db))
+	rg.GET("/trace-records/region-stats", read, traceRegionStats(db))
 	rg.GET("/trace-records/:id", read, getTraceRecord(db))
 	rg.POST("/trace-records", write, createTraceRecord(db))
 	rg.PATCH("/trace-records/:id", write, updateTraceRecord(db))
@@ -27,6 +29,33 @@ func RegisterTraceRoutes(rg *gin.RouterGroup, db *gorm.DB) {
 	rg.POST("/trace-records/:id/checklist", write, submitTraceChecklist(db))
 }
 
+// traceRegionStats 区域发病统计（近 N 天，按蚕房 region 聚合）
+func traceRegionStats(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		days := 90
+		if d, err := strconv.Atoi(c.DefaultQuery("days", "90")); err == nil && d > 0 && d <= 365 {
+			days = d
+		}
+		q := db.Table("trace_records").
+			Select("rooms.region AS region, trace_records.disease AS disease").
+			Joins("LEFT JOIN rooms ON rooms.id = trace_records.room_id").
+			Where("trace_records.created_at >= ?", time.Now().Add(-time.Duration(days)*24*time.Hour))
+		if disease := c.Query("disease"); disease != "" {
+			q = q.Where("trace_records.disease = ?", disease)
+		}
+		var rows []struct {
+			Region  string `gorm:"column:region"`
+			Disease string `gorm:"column:disease"`
+		}
+		q.Scan(&rows)
+		entries := make([]service.RegionDiseaseEntry, 0, len(rows))
+		for _, r := range rows {
+			entries = append(entries, service.RegionDiseaseEntry{Region: r.Region, Disease: r.Disease})
+		}
+		c.JSON(http.StatusOK, service.AggregateRegionStats(entries))
+	}
+}
+
 func listTraceRecords(db *gorm.DB) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		q := db.Model(&model.TraceRecord{})