normalize every song genre into song_genres

Split genre tags on Navidrome's separators (semicolon, slash, comma) and
resolve ID3v1 numeric indices to their names, so a song's genres are one
deduped list. songs.genre is now derived data with no reader: drop the
column and its index, and read the song info dialog's genres from
song_genres.

app/src/test/kotlin/com/subtracks/data/sync/Id3v1GenresTest.kt

@@ -0,0 +1,29 @@
+package com.subtracks.data.sync
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+class Id3v1GenresTest {
+    @Test
+    fun knownIndicesMapToTheirNames() {
+        assertEquals("Blues", id3v1Genre("0"))
+        assertEquals("Rock", id3v1Genre("17"))
+        assertEquals("Electronic", id3v1Genre("52"))
+        assertEquals("Psybient", id3v1Genre("191"))
+    }
+
+    @Test
+    fun parenthesisedAndPaddedIndicesMap() {
+        assertEquals("Rock", id3v1Genre("(17)"))
+        assertEquals("Rock", id3v1Genre(" 17 "))
+    }
+
+    @Test
+    fun unknownValuesAreLeftUnmapped() {
+        assertNull(id3v1Genre("192"))
+        assertNull(id3v1Genre("-1"))
+        assertNull(id3v1Genre("Rock"))
+        assertNull(id3v1Genre("17.0"))
+    }
+}

app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt

@@ -347,6 +347,94 @@ class SyncServiceTest {
             assertEquals(listOf("Rock"), db.libraryDao().songGenres(1, "s3").first())
         }
 
+    @Test
+    fun genresSplitOnEveryNavidromeSeparator() =
+        runTest {
+            insertSource()
+            val source =
+                FakeMusicSource(
+                    albums = listOf(album("al1")),
+                    songs =
+                        listOf(
+                            song("s1").copy(genre = "Classical;Minimal/Rock,Pop"),
+                            song("s2").copy(genres = listOf("Jazz/Blues", "Soul, Funk")),
+                        ),
+                )
+
+            SyncService(db, source).sync()
+
+            assertEquals(
+                listOf("Classical", "Minimal", "Rock", "Pop"),
+                db.libraryDao().songGenres(1, "s1").first(),
+            )
+            assertEquals(listOf("Jazz", "Blues", "Soul", "Funk"), db.libraryDao().songGenres(1, "s2").first())
+        }
+
+    @Test
+    fun numericGenresMapToId3v1Names() =
+        runTest {
+            insertSource()
+            val source =
+                FakeMusicSource(
+                    albums = listOf(album("al1")),
+                    songs =
+                        listOf(
+                            song("s1").copy(genre = "17"),
+                            song("s2").copy(genre = "(52)"),
+                            song("s3").copy(genre = "999"),
+                        ),
+                )
+
+            SyncService(db, source).sync()
+
+            assertEquals(listOf("Rock"), db.libraryDao().songGenres(1, "s1").first())
+            assertEquals(listOf("Electronic"), db.libraryDao().songGenres(1, "s2").first())
+            assertEquals(listOf("999"), db.libraryDao().songGenres(1, "s3").first())
+        }
+
+    @Test
+    fun genresThatMapToTheSameNameCollapse() =
+        runTest {
+            insertSource()
+            val source =
+                FakeMusicSource(
+                    albums = listOf(album("al1")),
+                    songs =
+                        listOf(
+                            song("s1").copy(genre = "17;Rock"),
+                            song("s2").copy(genres = listOf("17", "Rock")),
+                        ),
+                )
+
+            SyncService(db, source).sync()
+
+            assertEquals(listOf("Rock"), db.libraryDao().songGenres(1, "s1").first())
+            assertEquals(listOf("Rock"), db.libraryDao().songGenres(1, "s2").first())
+        }
+
+    @Test
+    fun concatenatedAndIndividualGenresCollapseOnTheHomeFeed() =
+        runTest {
+            insertSource()
+            val source =
+                FakeMusicSource(
+                    albums = listOf(album("al1")),
+                    songs =
+                        listOf(
+                            song("s1").copy(genre = "Classical;Minimal"),
+                            song("s2").copy(genre = "Classical"),
+                            song("s3").copy(genre = "Minimal"),
+                        ),
+                )
+
+            SyncService(db, source).sync()
+
+            assertEquals(
+                listOf("Classical", "Minimal"),
+                db.libraryDao().genresByMostPlayed(1).first(),
+            )
+        }
+
     @Test
     fun thePluralGenresWinOverTheSingularAttribute() =
         runTest {