feat: dynamic user idle_timeout from patch.cfg without container restart

When user.idle_timeout is present in patch.cfg, apply_patch_config() now
updates all active user sessions via usr::update_idle_timeout() and also
updates the cached metric_thresholds array for future connections.

Previously user.idle_timeout was only read at startup (usr::init()) and could
not be changed on a running node without a container restart.

Implementation:
- comm_server.hpp: added for_each_session() template to iterate live sessions
  (shared with feat/dynamic-mesh-idle-timeout-from-patch-cfg)
- usr.cpp: added update_idle_timeout() which updates metric_thresholds[4] and
  calls set_threshold(IDLE_CONNECTION_TIMEOUT) on all active user sessions
- conf.cpp: reads user.idle_timeout from patch.cfg in apply_patch_config(),
  calls usr::update_idle_timeout() when value changes

Sibling PRs (part of dynamic config series):
- fix/dynamic-log-level-from-patch-cfg (already raised)
- feat/dynamic-mesh-idle-timeout-from-patch-cfg (already raised)

src/conf.cpp

@@ -7,6 +7,9 @@
 #include "ledger/ledger_mount.hpp"
 #include "sc/contract_mount.hpp"
 
+// Forward declaration to avoid circular dependency with usr/usr.hpp
+namespace usr { void update_idle_timeout(const uint32_t timeout_ms); }
+
 namespace conf
 {
 
@@ -853,6 +856,21 @@ namespace conf
             return -1;
         }
 
+        // Apply user idle timeout change dynamically if present in patch config.
+        // Updates all active user sessions and future connections without restart.
+        try {
+            if (jdoc.contains("user") && jdoc["user"].contains("idle_timeout")) {
+                const uint32_t new_idle_timeout = jdoc["user"]["idle_timeout"].as<uint32_t>();
+                if (new_idle_timeout != cfg.user.idle_timeout) {
+                    cfg.user.idle_timeout = new_idle_timeout;
+                    temp_cfg.user.idle_timeout = new_idle_timeout;
+                    usr::update_idle_timeout(new_idle_timeout);
+                    LOG_INFO << "User idle timeout updated dynamically to: " << new_idle_timeout << "ms";
+                }
+            }
+        } catch (const std::exception &e) {
+            LOG_ERROR << "Error applying user idle timeout from patch config: " << e.what();
+        }
         LOG_INFO << "Contract config updated from patch file.";
         return 0;
     }

src/usr/usr.cpp

@@ -74,6 +74,24 @@ namespace usr
         }
     }
 
+    /**
+     * Update user idle timeout on all active user sessions and for future connections.
+     * Called from conf::apply_patch_config() when user.idle_timeout changes in patch.cfg.
+     * Updates both the cached metric_thresholds array (for new sessions) and all
+     * existing live sessions via set_threshold() so no restart is required.
+     */
+    void update_idle_timeout(const uint32_t timeout_ms)
+    {
+        metric_thresholds[4] = timeout_ms;
+        if (ctx.server.has_value())
+        {
+            ctx.server->for_each_session([timeout_ms](user_comm_session &session) {
+                session.set_threshold(comm::SESSION_THRESHOLDS::IDLE_CONNECTION_TIMEOUT, timeout_ms, 60000);
+            });
+            LOG_INFO << "User idle timeout updated dynamically to: " << timeout_ms << "ms";
+        }
+    }
+
     /**
      * Starts listening for incoming user websocket connections.
      */