feat: 引入可切换星历模型并扩展天象观测链路

- 新增半解析、旧模型、自定义与多源堆叠星历实例，提供 Context、Instance、SPK 读取及状态与视位置计算
- 统一太阳、月球和行星实例接口，扩展黄经穿越、留、相位、最近角距、偕日可见、任意高度升落、轨道节点及凌日等天象查询
- 完善日月食、月掩与凌日的月缘剖面、有限盘面接触、站心修正、局地可见性、全球路径和地图输出
- 新增 SVG、GeoJSON、KML 天象输出及凌日、月掩和月缘地形相关缓存与几何求解
- 新增恒星星表导入与查询，支持 CSV、Hipparcos、BSC5、Stellarium 等格式及名称、交叉标识、锥面检索和星等过滤
- 补充 IAU 2006、地球定向、折射消光、大气观测、轨道传播及半解析行星/月球数据支持
- 将默认未来民用时标切换为 TimeScaleLeapHour，更新 2027–2400 农历速查表、中文日期解析和时区边界处理
- 增加事件基线、跨模型回归、几何边界、月缘地形和输出契约测试，完善中英文手册、示例资源、NOTICE 与忽略规则

internal/timenote/timenote.go

@@ -7,15 +7,15 @@ import (
 	"strings"
 	"time"
 
-	"b612.me/astro"
+	"b612.me/astro/basic"
 )
 
 const english = "en"
 
 // Scale 生成图内时标声明：UTC 口径写显示时区与 UTC 偏移，UT1 口径补 DUT1 差值 / builds the in-figure time-scale declaration.
-func Scale(scale astro.TimeScale, instant time.Time, location *time.Location, language string) string {
-	if scale == astro.TimeScaleUT1 {
-		dut1 := astro.DUT1(instant)
+func Scale(scale basic.TimeScale, instant time.Time, location *time.Location, language string) string {
+	if scale == basic.TimeScaleUT1 {
+		dut1 := basic.DUT1(instant)
 		if language == english {
 			return fmt.Sprintf("Times are UT1 (Universal Time 1); DUT1 = UT1−UTC = %+.2f s.", dut1)
 		}

internal/timenote/timenote_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 	"time"
 
-	"b612.me/astro"
+	"b612.me/astro/basic"
 )
 
 // 时标声明里同一个 UTC 偏移只写一次：时区名本身是偏移标签（FixedZone("UTC+08:00") 之类）时不再追加偏移。
@@ -27,7 +27,7 @@ func TestScaleWritesTheOffsetOnce(t *testing.T) {
 		{name: "UTC", location: time.UTC, want: "图中时刻为 UTC"},
 	} {
 		t.Run(test.name, func(t *testing.T) {
-			got := Scale(astro.TimeScaleUTC, instant, test.location, test.language)
+			got := Scale(basic.TimeScaleUTC, instant, test.location, test.language)
 			if got != test.want {
 				t.Fatalf("Scale() = %q, want %q", got, test.want)
 			}