feat(mining): host a RandomX stratum pool from the node (v1.3.0+)

Add an opt-in "Host a mining pool (stratum)" toggle so a v1.3.0+ node can run its native
RandomX stratum server for other miners to point at. Settings toggle + optional allow-IP/CIDR;
passes -stratum (+ -stratumallowip) to the daemon launch args, mirroring the -maxconnections
plumbing (EmbeddedDaemon::setStratumHosting <- DaemonController::syncSettings <- Settings).

Backwards compatible / safe by default:
- UI gated on daemon_version >= 1030000, so it's never offered where it would do nothing.
- The launch flag is harmless on older daemons (they ignore unknown args), and the toggle can
  only be enabled while connected to a v1.3.0+ node anyway.
- Blank allow-IP => the daemon serves loopback only (its safe default); entering a subnet opens
  it to that LAN, with an explicit exposure warning in the UI.
- Takes effect on the next daemon start/restart.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/daemon/daemon_controller.cpp

@@ -26,6 +26,7 @@ void DaemonController::syncSettings(const config::Settings* settings)
     if (!settings) return;
     daemon_->setDebugCategories(settings->getDebugCategories());
     daemon_->setMaxConnections(settings->getMaxConnections());
+    daemon_->setStratumHosting(settings->getStratumHost(), settings->getStratumAllowIp());
 
     std::string walletFile = settings->getActiveWalletFile();
     // The Wallets dialog opens an out-of-datadir wallet by linking it into the datadir under a