feat(data): 多源星历按历元取最新（对齐上游），源顺序只影响卫星名

采用上游 6f3e3351 的合并口径：同一 NORAD 号的轨道元素取历元最新者，名字取
列表中第一个提供该星的源，源顺序因此退化为命名偏好。fork 此前是
flatMap + distinctBy{catnum}（列表靠前者全胜）——实测 R4UAB 的元素平均比
CelesTrak 旧 8.4h（78 颗共有业余星中 67 颗更旧），却因排在列表前面而抢占。

- OrbitalData：暴露 epochDaynum / timeToDaynum / epochToDaynum（跨源比较必须
  走 daynum，原始 YYDDD 跨十年不可比）
- DatabaseRepo：新增 mergeEntries（历元最新元素 + 首个提供者的名字）、
  insertFresherEntries（只写入更新过的元素，并对未更新者原地改名，使重排源
  顺序立即生效）、pruneStaleEntries（30 天无源刷新的星清理）
- updateFromRemote 改为按源分别解析；保留 fork 的 importedTypeIds 类型映射
  （按每源结果统计，供筛选 chips 与自定义源使用）；全部源失败时保留上次成功
  时间戳，下次启动重试
- updateTLEFromFile 走同一合并链路（手工导入同样只升不降）
- 新增 5 个单测（含 prune 与失败保时间戳），fixture 历元改为当前（旧历元
  会被新 prune 规则清掉）；两个 fake 补齐 ILocalSource 新接口

测试：core:domain 171 / core:data 121 全绿。

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/predict/OrbitalData.kt

@@ -37,30 +37,42 @@ data class OrbitalData(
     val xno: Double = meanmo * TWO_PI / MIN_PER_DAY
     val orbitalPeriod: Double = MIN_PER_DAY / meanmo
     val isDeepSpace: Boolean = orbitalPeriod >= 225.0 // NearEarth (period < 225 min) or DeepSpace (period >= 225 min)
+
+    /** Absolute age of this element set, used to pick the freshest data among several sources. */
+    val epochDaynum: Double = epochToDaynum(epoch)
+
     fun getObject(): OrbitalObject = if (isDeepSpace) DeepSpaceObject(this) else NearEarthObject(this)
 
     /** Check if satellite has likely decayed by the given time. */
     fun hasDecayed(currentTimeMillis: Long): Boolean {
         if (ndot == 0.0) return false
-        val currentDaynum = (currentTimeMillis - 315446400000L) / 86400000.0
-        val epochDaynum = epochToDaynum(epoch)
-        return CelestialComputer.hasDecayed(meanmo, ndot, epochDaynum, currentDaynum)
+        return CelestialComputer.hasDecayed(meanmo, ndot, epochDaynum, timeToDaynum(currentTimeMillis))
     }
 
-    private fun epochToDaynum(epoch: Double): Double {
-        var year = kotlin.math.floor(epoch * 1E-3)
-        val day = (epoch * 1E-3 - year) * 1000.0
-        year = if (year < 57) year + 2000 else year + 1900
-        // daynum = days since 31 Dec 1979, Julian date of 31Dec79 = 2444238.5
-        val jan1Jd = julianDateOfYear(year)
-        return jan1Jd + day - 2444238.5
-    }
+    companion object {
+        /** Days since 31 Dec 1979, the reference point every daynum in the app is based on. */
+        fun timeToDaynum(timeMillis: Long): Double = (timeMillis - 315446400000L) / 86400000.0
 
-    private fun julianDateOfYear(theYear: Double): Double {
-        val aYear = theYear - 1
-        val a = kotlin.math.floor(aYear / 100).toLong()
-        val b = 2 - a + a / 4
-        val i = kotlin.math.floor(365.25 * aYear).toLong()
-        return i + (30.6001 * 14).toLong() + 1720994.5 + b
+        /**
+         * Days since 31 Dec 1979 for a TLE style YYDDD.ffffffff epoch. Raw epochs are not
+         * comparable across decades (a 1999 epoch reads as 99xxx, a 2026 one as 26xxx), so
+         * freshness checks must always go through this conversion.
+         */
+        fun epochToDaynum(epoch: Double): Double {
+            var year = kotlin.math.floor(epoch * 1E-3)
+            val day = (epoch * 1E-3 - year) * 1000.0
+            year = if (year < 57) year + 2000 else year + 1900
+            // daynum = days since 31 Dec 1979, Julian date of 31Dec79 = 2444238.5
+            val jan1Jd = julianDateOfYear(year)
+            return jan1Jd + day - 2444238.5
+        }
+
+        private fun julianDateOfYear(theYear: Double): Double {
+            val aYear = theYear - 1
+            val a = kotlin.math.floor(aYear / 100).toLong()
+            val b = 2 - a + a / 4
+            val i = kotlin.math.floor(365.25 * aYear).toLong()
+            return i + (30.6001 * 14).toLong() + 1720994.5 + b
+        }
     }
 }

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/source/ILocalSource.kt

@@ -26,6 +26,10 @@ interface ILocalSource {
     suspend fun getEntriesTotal(): Int
     suspend fun getEntriesList(): List<SatItem>
     suspend fun getEntriesWithIds(ids: List<Int>): List<OrbitalObject>
+    suspend fun getEntriesEpochs(): Map<Int, Double>
+    suspend fun getEntriesNames(): Map<Int, String>
+    suspend fun renameEntries(names: Map<Int, String>)
+    suspend fun deleteEntriesWithIds(ids: List<Int>)
     suspend fun insertEntries(entries: List<OrbitalData>)
     suspend fun deleteEntries()
     suspend fun getIdsWithModes(modes: List<String>): List<Int>