fix: add 30s timeout to API calls and catchError fallback on schedule load

Without a timeout, a hanging backend request left the schedule page showing
an infinite spinner forever. Timeout ensures any hung request fails fast and
the spinner resolves. The catchError fallback in schedule_view handles the
edge case where getProfessional rejects unexpectedly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/services/api_service.dart

@@ -30,8 +30,10 @@ class ApiService {
     throw Exception(body['message'] ?? 'Error ${res.statusCode}');
   }
 
+  static const _timeout = Duration(seconds: 30);
+
   Future<dynamic> get(String path) async {
-    final res = await http.get(Uri.parse('$baseUrl$path'), headers: await _headers());
+    final res = await http.get(Uri.parse('$baseUrl$path'), headers: await _headers()).timeout(_timeout);
     return _parse(res);
   }
 
@@ -40,7 +42,7 @@ class ApiService {
       Uri.parse('$baseUrl$path'),
       headers: await _headers(),
       body: jsonEncode(body),
-    );
+    ).timeout(_timeout);
     return _parse(res);
   }
 
@@ -49,12 +51,12 @@ class ApiService {
       Uri.parse('$baseUrl$path'),
       headers: await _headers(),
       body: jsonEncode(body),
-    );
+    ).timeout(_timeout);
     return _parse(res);
   }
 
   Future<dynamic> delete(String path) async {
-    final res = await http.delete(Uri.parse('$baseUrl$path'), headers: await _headers());
+    final res = await http.delete(Uri.parse('$baseUrl$path'), headers: await _headers()).timeout(_timeout);
     return _parse(res);
   }