Remove flutter chat (#26)

Had to squash merge manually as Forgejo was erroring

lib/widgets/composer/relation_preview.dart

@@ -0,0 +1,70 @@
+import "package:flutter/material.dart";
+import "package:hooks_riverpod/hooks_riverpod.dart";
+import "package:nexus/models/event.dart";
+import "package:nexus/models/relation_type.dart";
+import "package:nexus/widgets/event_preview.dart";
+
+class RelationPreview extends ConsumerWidget {
+  final Event? relatedEvent;
+  final RelationType relationType;
+  final VoidCallback onDismiss;
+  final bool shouldMention;
+  final VoidCallback toggleShouldMention;
+
+  const RelationPreview(
+    this.relatedEvent, {
+    required this.relationType,
+    required this.onDismiss,
+    required this.shouldMention,
+    required this.toggleShouldMention,
+    super.key,
+  });
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    if (relatedEvent == null) return SizedBox.shrink();
+    final theme = Theme.of(context);
+
+    return Container(
+      color: theme.colorScheme.surfaceContainerHigh,
+      padding: EdgeInsets.symmetric(horizontal: 12),
+      child: Row(
+        spacing: 8,
+        children: [
+          if (relationType == RelationType.edit)
+            Text(
+              "Editing message:",
+              style: TextStyle(fontWeight: FontWeight.bold),
+            ),
+
+          Expanded(
+            child: Padding(
+              padding: EdgeInsets.symmetric(vertical: 8),
+              child: EventPreview(relatedEvent!),
+            ),
+          ),
+
+          if (relationType == RelationType.reply)
+            TextButton(
+              onPressed: toggleShouldMention,
+              child: Text(
+                shouldMention ? "@On" : "@Off",
+                style: TextStyle(
+                  fontWeight: FontWeight.w900,
+                  color: shouldMention ? null : Theme.of(context).disabledColor,
+                ),
+              ),
+            ),
+
+          IconButton(
+            tooltip:
+                "Cancel ${relationType == RelationType.edit ? "edit" : "reply"}",
+            onPressed: onDismiss,
+            icon: const Icon(Icons.close),
+            iconSize: 20,
+          ),
+        ],
+      ),
+    );
+  }
+}