feat(settings): custom URL now overrides the online-update default source

The "Custom URL" dialog's two URL fields now control the default
source used by the online update, per the user's intent (one-time
setup, no extra steps per update):

- Defaults are real URLs now: TLE = Celestrak "All" (active group
  CSV), transceivers = SatNOGS API. The example.com placeholders are
  gone.
- updateFromRemote(): the "All" TLE entry and the "SatNOGS" entry are
  replaced by the user's URLs when the corresponding custom toggle is
  ON and the URL is non-blank; otherwise the real defaults are used.
  The old "Other" appended-source logic is removed - the toggle now
  means "use my URL for this source" instead of "download an extra
  source". Each source (TLE / transceivers) is independent.
- Each URL field gained a reset (loop) icon button on the right that
  restores the default URL text (new ic_reset drawable, Autorenew
  vector). Strings added in en/zh/tr.

Test updated: custom TLE URL data now lands under the "All" type
instead of "Other". Verified: core:data tests pass, settings + app
compile. Version stays 4.4.8 (覆盖 per user).

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

@@ -18,6 +18,10 @@
 package com.rtbishop.look4sat.core.domain.source
 
 object Sources {
+    // 在线更新的默认 URL(用户可通过"自定义URL"对话框修改/重置)
+    val defaultTleUrl = "https://celestrak.org/NORAD/elements/gp.php?GROUP=active&FORMAT=csv"
+    val defaultTransceiversUrl = "https://db.satnogs.org/api/transmitters/?format=json&status=active"
+
     val satelliteDataUrls = mapOf(
         "All" to "https://celestrak.org/NORAD/elements/gp.php?GROUP=active&FORMAT=csv",
         "Amateur" to "https://celestrak.org/NORAD/elements/gp.php?GROUP=amateur&FORMAT=csv",