treewide(refactor): rename files to follow the same style

lib/controllers/event.dart

@@ -0,0 +1,32 @@
+import "package:collection/collection.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/controllers/rooms.dart";
+import "package:nexus/models/event.dart";
+import "package:nexus/models/requests/get_event.dart";
+
+class EventController extends AsyncNotifier<Event?> {
+  final GetEventRequest request;
+  EventController(this.request);
+
+  @override
+  Future<Event?> build() async {
+    final room = ref.watch(
+      RoomsController.provider.select((value) => value[request.roomId]),
+    );
+    final event = room?.events.values.firstWhereOrNull(
+      (event) => event.eventId == request.eventId,
+    );
+
+    return event ??
+        await ref
+            .watch(ClientController.provider.notifier)
+            .getEvent(request)
+            .onError((_, _) => null);
+  }
+
+  static final provider = AsyncNotifierProvider.family
+      .autoDispose<EventController, Event?, GetEventRequest>(
+        EventController.new,
+      );
+}