refactor(amsat): align with Material3 conventions per PR #233 review

Addresses feedback from rt-bishop/Look4Sat#233:

1. Migrate hardcoded colors to MainTheme colorScheme
   - Extend darkScheme: tertiary (Active 0xFF648FFF), tertiaryContainer (Telemetry 0xFFFFB000)
   - Extend lightScheme: tertiary (0xFF3C6FE0), tertiaryContainer (0xFFE09800) for contrast
   - Remove top-level Color() constants from SatStatusScreen.kt
   - Add statusColorOf() mapper using MaterialTheme.colorScheme

2. Move HTTP implementation from domain to data layer (Clean Architecture)
   - Delete AmSatApiClient.kt from core:domain (violates AGENTS.md: "Pure Kotlin, NO Android deps")
   - Migrate to IRemoteSource/RemoteSource in core:data (uses existing OkHttp3)
   - AmSatRepository now depends on IRemoteSource instead of AmSatApiClient

3. Inline JSON parsing (prepare for java.time migration)
   - Parse AMSAT API responses (names, reports) in AmSatRepository
   - Time parsing still uses manual logic (java.time desugaring in follow-up)

Before:
  - Hardcoded Color(0xFFXXXXXX) in UI + Repository (no theme support)
  - HttpURLConnection in domain layer (architecture violation)
  - AMSAT colors duplicated across modules

After:
  - MaterialTheme.colorScheme.tertiary/tertiaryContainer (light/dark adaptive)
  - HTTP via data layer RemoteSource (follows AGENTS.md architecture)
  - Single source of truth for AMSAT colors

Ref: https://github.com/rt-bishop/Look4Sat/pull/233#discussion_r1868599947
Ref: AGENTS.md "core:domain - Pure Kotlin (JVM). NO Android dependencies."

core/presentation/src/main/java/com/rtbishop/look4sat/core/presentation/MainTheme.kt

@@ -79,6 +79,10 @@ private val lightScheme = lightColorScheme(
     onSecondary = Color(0xFFFFFFFF),
     secondaryContainer = Color(0xFFF1E1BB),
     onSecondaryContainer = Color(0xFF221B04),
+    tertiary = Color(0xFF3C6FE0), // AMSAT Active (darker for light theme)
+    onTertiary = Color(0xFFFFFFFF),
+    tertiaryContainer = Color(0xFFE09800), // AMSAT Telemetry (darker)
+    onTertiaryContainer = Color(0xFF000000),
     background = Color(0xFFFFF8F0),
     onBackground = Color(0xFF1E1B13),
     surface = Color(0xFFFFF8F0),
@@ -101,10 +105,10 @@ private val darkScheme = darkColorScheme(
     onSecondary = Color(0xFF000000),
     secondaryContainer = Color(0xFF404040), // navBar indicator,
     onSecondaryContainer = Color(0xFFE0E0E0), // navBar active icon
-//    tertiary = Color(0xFF121212),
-//    onTertiary = Color(0xFF121212),
-//    tertiaryContainer = Color(0xFF121212),
-//    onTertiaryContainer = Color(0xFF121212),
+    tertiary = Color(0xFF648FFF), // AMSAT Active (from amsat.org/status)
+    onTertiary = Color(0xFF000000),
+    tertiaryContainer = Color(0xFFFFB000), // AMSAT Telemetry
+    onTertiaryContainer = Color(0xFF000000),
     background = Color(0xFF121212),
     onBackground = Color(0xFFE0E0E0),
     surface = Color(0xFF202020), // card background