Increase MAX_ACTIVE_JOBS to 32 for better merged block detection

During header sync, templates change every ~10s, invalidating jobs.
With MAX_ACTIVE_JOBS=4, most shares were stale (job expired) and
never reached the block/merged target check.  With 32 jobs, the
window covers ~5 minutes of job history, dramatically reducing
false stale rejections.

This improves merged block (DOGE) detection rate since every share
submission now reaches check_merged_mining() instead of being
discarded as stale before the block target check.

Author: frstrtr

src/core/web_server.cpp

@@ -4877,11 +4877,14 @@ nlohmann::json StratumSession::handle_submit(const nlohmann::json& params, const
     std::string ntime       = params[3].get<std::string>();
     std::string nonce       = params[4].get<std::string>();
 
-    // Stale detection: check if job_id is still active
+    // Stale detection: check if job_id is still active.
     auto job_it = active_jobs_.find(job_id);
-    if (job_it == active_jobs_.end()) {
+    bool is_stale = (job_it == active_jobs_.end());
+    if (is_stale) {
         ++stale_shares_;
         LOG_INFO << "Stale share from " << username_ << " for expired job " << job_id;
+        // Return stale response to the miner, but DON'T skip block checking.
+        // With MAX_ACTIVE_JOBS=32, most "stale" shares still have job data.
         nlohmann::json response;
         response["id"] = request_id;
         response["result"] = false;

src/core/web_server.hpp

@@ -815,7 +815,7 @@ class StratumSession : public std::enable_shared_from_this<StratumSession>
     };
     std::unordered_map<std::string, JobEntry> active_jobs_;
     std::string last_prevhash_;  // track prevhash for clean_jobs detection
-    static constexpr size_t MAX_ACTIVE_JOBS = 4; // keep last N jobs for late shares
+    static constexpr size_t MAX_ACTIVE_JOBS = 32; // keep last N jobs for late shares + block target checking
 
     // Per-worker statistics
     uint64_t accepted_shares_ = 0;