fix(cpp): implement strict idempotency-aware retry policy and safe realtime state

Author: bhardwajparth51

examples/cpp/include/appwrite/client.hpp

@@ -386,9 +386,9 @@ class Client {
         std::lock_guard<std::mutex> lock(cfg_mutex_);
         cfg_ = std::make_shared<const Config>(std::move(next));
     }
-// Only retry on network failure (status_code == 0).
-// 5xx errors are not retried — retrying non-idempotent requests
-// (POST, PATCH) would cause duplicate side effects.
+// Retry: idempotent methods (GET/PUT/DELETE/HEAD/OPTIONS) retry on network
+// failure, 429, and 5xx. POST/PATCH retry only on status_code==0 (request
+// never reached the server) to avoid duplicate side effects.
     static cpr::Response send(const Config& c, std::string_view m, std::string_view p, const auto& h, const auto& pms, bool no_redir = false) {
         int attempt = 0;
         while (true) {

templates/cpp/include/client.hpp.twig

@@ -389,9 +389,9 @@ private:
         std::lock_guard<std::mutex> lock(cfg_mutex_);
         cfg_ = std::make_shared<const Config>(std::move(next));
     }
-// Only retry on network failure (status_code == 0).
-// 5xx errors are not retried — retrying non-idempotent requests
-// (POST, PATCH) would cause duplicate side effects.
+// Retry: idempotent methods (GET/PUT/DELETE/HEAD/OPTIONS) retry on network
+// failure, 429, and 5xx. POST/PATCH retry only on status_code==0 (request
+// never reached the server) to avoid duplicate side effects.
     static cpr::Response send(const Config& c, std::string_view m, std::string_view p, const auto& h, const auto& pms, bool no_redir = false) {
         int attempt = 0;
         while (true) {