feat: 完善时标与天象几何计算并扩展输出接口

- 新增时标、ΔT 模型、质心时间与 UT1 支持
- 改进日月食、月掩、行星事件及路径边界计算
- 完善恒星三维自行与动态距离传播
- 扩展 SVG、GeoJSON、KML 输出与底层距离换算工具
- 整理中英文手册、示例资源及回归测试

basic/occultation_planet.go

@@ -370,7 +370,7 @@ func planetMoonPositionAt(tt float64, config planetOccultationConfig, observer *
 	moonRA, moonDec := HMoonGeocentricApparentRaDecN(tt, n)
 	planetRA, planetDec := config.apparentRaDecN(tt, n)
 	if observer != nil {
-		ut := TD2UT(tt, false)
+		ut := TT2UTC(tt)
 		moonDistanceAU := HMoonAwayN(tt, n) / angularDiameterAstronomicalUnitKM
 		planetDistanceAU := config.earthDistanceN(tt, n)
 		moonRA, moonDec = TopocentricRaDec(moonRA, moonDec, observer.Latitude, observer.Longitude, ut, moonDistanceAU, observer.Height)
@@ -425,7 +425,7 @@ func planetTopocentricSemidiameterN(tt float64, config planetOccultationConfig,
 	if !finite(ra) || !finite(dec) || !finite(distanceKM) || distanceKM <= 0 {
 		return math.NaN()
 	}
-	distanceKM = topocentricDistanceKM(ra, dec, distanceKM, observer, TD2UT(tt, false))
+	distanceKM = topocentricDistanceKM(ra, dec, distanceKM, observer, TT2UTC(tt))
 	if !finite(distanceKM) || distanceKM <= config.equatorialRadiusKM {
 		return math.NaN()
 	}