Remove flutter chat (#26)

Had to squash merge manually as Forgejo was erroring

lib/widgets/html/mention_chip.dart

@@ -0,0 +1,53 @@
+import "package:flutter/material.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/user_controller.dart";
+import "package:nexus/helpers/extensions/link_to_mention.dart";
+import "package:nexus/helpers/extensions/show_user_popover.dart";
+import "package:nexus/models/configs/user_config.dart";
+
+class MentionChip extends ConsumerWidget {
+  final String? roomId;
+  final String content;
+  const MentionChip(this.content, this.roomId, {super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final mention = content.mention;
+    final membership = mention?.startsWith("@") == true
+        ? ref
+              .watch(
+                UserController.provider(
+                  UserConfig(roomId: roomId, userId: mention!),
+                ),
+              )
+              .whenOrNull(data: (data) => data)
+        : null;
+
+    return mention == null
+        ? SizedBox.shrink()
+        : InkWell(
+            onTapUp: (details) {
+              if (membership != null) {
+                context.showUserPopover(
+                  membership,
+                  mention,
+                  globalPosition: details.globalPosition,
+                );
+              }
+            },
+            child: IgnorePointer(
+              child: Chip(
+                label: Text(
+                  (membership == null ? null : "@${membership.displayName}") ??
+                      mention,
+                  style: TextStyle(
+                    fontWeight: FontWeight.bold,
+                    color: Theme.of(context).colorScheme.onPrimary,
+                  ),
+                ),
+                backgroundColor: Theme.of(context).colorScheme.primary,
+              ),
+            ),
+          );
+  }
+}