refactored HTTP error handling and streamlined UI components by centralizing shared logic and removing redundant parameters

lib/api/http_errors.dart

@@ -0,0 +1,53 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:http/http.dart' as http;
+
+import 'errors/auth_exception.dart';
+import 'errors/network_exception.dart';
+import 'errors/not_found_exception.dart';
+import 'errors/server_exception.dart';
+
+/// Runs [send] and converts transport-level failures (socket/timeout/client
+/// errors) into a [NetworkException] tagged with [label] (e.g. `Talk <uri>`).
+/// Passes through whatever [send] produces, including `null` for the base-class
+/// request hooks that may skip the call.
+Future<http.Response?> sendGuarded(
+  String label,
+  Future<http.Response>? Function() send,
+) async {
+  try {
+    return await send();
+  } on SocketException catch (e) {
+    throw NetworkException(technicalDetails: '$label: ${e.message}');
+  } on TimeoutException catch (e) {
+    throw NetworkException.timeout(technicalDetails: '$label: $e');
+  } on http.ClientException catch (e) {
+    throw NetworkException(technicalDetails: '$label: ${e.message}');
+  }
+}
+
+/// Collapses whitespace and caps an HTTP error body at 500 chars so it can be
+/// embedded in an [AppException]'s technical details without dumping headers.
+String previewBody(String body) {
+  final collapsed = body.replaceAll(RegExp(r'\s+'), ' ').trim();
+  return collapsed.length > 500 ? '${collapsed.substring(0, 500)}…' : collapsed;
+}
+
+/// Builds a `<label> -> HTTP <status>[ body=<preview>]` technical detail line.
+String httpErrorDetail(String label, String body, int status) {
+  final preview = previewBody(body);
+  return preview.isEmpty
+      ? '$label -> HTTP $status'
+      : '$label -> HTTP $status body=$preview';
+}
+
+/// Throws the [AppException] matching a non-2xx HTTP [status], carrying
+/// [detail] as technical details: 401/403 map to auth errors, 404 to
+/// not-found, everything else to a generic server error.
+Never throwForStatus(int status, String detail) {
+  if (status == 401) throw AuthException.unauthorized(technicalDetails: detail);
+  if (status == 403) throw AuthException.forbidden(technicalDetails: detail);
+  if (status == 404) throw NotFoundException(technicalDetails: detail);
+  throw ServerException(statusCode: status, technicalDetails: detail);
+}