fix(metadata): recognize featured artist credits consistently

Handle feature and featured separators across display, Android finalization and Rust tag writing. Split conjunction credits only when separate artist IDs confirm them, and offer a picker for multi-artist navigation.

android/app/src/test/kotlin/com/zarz/spotiflac/NativeFinalizationPolicyTest.kt

@@ -18,6 +18,8 @@ class NativeFinalizationPolicyTest {
             "Artist A Feat Artist B" to "Artist A",
             "Artist A ft. Artist B" to "Artist A",
             "Artist A featuring Artist B" to "Artist A",
+            "Artist A featured Artist B" to "Artist A",
+            "Artist A feature Artist B" to "Artist A",
             "Artist A with Artist B" to "Artist A",
             "Artist A x Artist B" to "Artist A",
             "Artist A X Artist B" to "Artist A",