bring in database

switch to just using source models (no extra db fields)
start re-implementing sync service

test/util/database.dart

@@ -0,0 +1,10 @@
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:subtracks/database/database.dart';
+
+SubtracksDatabase testDatabase() => SubtracksDatabase(
+  DatabaseConnection(
+    NativeDatabase.memory(),
+    closeStreamsSynchronously: true,
+  ),
+);