feat(mining): auto-balance driver, per-pool algo, live miner version

- app: periodic weighted-random auto-balance of the pool while pool-mining
  (~30-min cadence; restarts the miner only when the pick actually changes),
  plus snapshot + refresh accessors for the UI.
- app_network: resolve the xmrig algo per pool at start (pool.dragonx.cc =
  rx/dragonx, pool.dragonx.is = rx/hush; custom hosts keep the setting).
- xmrig_manager: schema-aware pool-side hashrate readout (fixes a silent 0 for
  Miningcore pools); expose the running miner's version from its HTTP API and a
  cached `xmrig --version` detection so the UI can show it before mining.
- wallet_state: carry the running miner's version.

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

src/data/wallet_state.h

@@ -170,6 +170,7 @@ struct PoolMiningState {
     bool   xmrig_running = false;
     std::string pool_url;
     std::string algo;
+    std::string version;            // running miner's version (from its API)
 
     double hashrate_10s  = 0;
     double hashrate_60s  = 0;