feat: 完善日月食与月掩几何链路并扩展历法接口

- 新增日月食中心带、偏食带、阴影足迹、等时线、食分线及升落边界计算，支持极区与混合食拓扑
- 新增日食单时刻阴影求解器、站心状态查询、批量采样和 ΔT 覆盖接口
- 重构恒星与行星月掩路径，补充有限盘面接触、站心修正、掩带宽度、极区投影及升落边界
- 扩展 SVG 与 GeoJSON 输出，支持详细面板、全球/极区/地球投影、边界闭合、时间标记和拓扑签名
- 扩展日月食候选搜索、局地搜索、沙罗序列预计算与范围外推，补充系列锚点和成员一致性校验
- 补齐古历纪年、儒略历独有闰日、多公历候选、历法改革跨日及精确日期运算接口
- 优化 ΔT、章动、恒星时、月球地平线、事件根搜索和本地星历缓存，降低重复计算开销并提升边界稳定

eclipse/observation_helpers.go

@@ -46,5 +46,19 @@ func lunarCulminationTime(date time.Time, lon, lat float64) time.Time {
 	}
 	jde := basic.Date2JDE(date)
 	_, loc := date.Zone()
-	return basic.JDE2DateByZone(basic.MoonCulminationTime(jde, lon, lat, float64(loc)/3600.0), date.Location(), true)
+	culmination := basic.JDE2DateByZone(basic.MoonCulminationTime(jde, lon, lat, float64(loc)/3600.0), date.Location(), true)
+	// MoonCulminationTime returns the nearest root to its internal midnight
+	// seed, which can land one civil day later when the input is local noon.
+	// Visibility scans need the root belonging to the supplied local day.
+	if culmination.Year() != date.Year() || culmination.YearDay() != date.YearDay() {
+		// Preserve the solved local clock time while moving it onto the
+		// requested civil date. This also avoids assuming every DST day is
+		// exactly 24 elapsed hours.
+		culmination = time.Date(
+			date.Year(), date.Month(), date.Day(),
+			culmination.Hour(), culmination.Minute(), culmination.Second(), culmination.Nanosecond(),
+			date.Location(),
+		)
+	}
+	return culmination
 }