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/daemon/xmrig_manager.h

@@ -43,6 +43,7 @@ public:
         double  pool_diff    = 0;
         std::string pool_url;
         std::string algo;
+        std::string version;      // miner version reported by the running xmrig API
         bool connected       = false;
         // Memory usage
         int64_t memory_free  = 0;   // bytes
@@ -137,6 +138,18 @@ public:
      */
     static std::string findXmrigBinary();
 
+    /**
+     * @brief Kick a one-shot background `<binary> --version` detection (idempotent).
+     * Lets the UI show the installed miner's version before mining is ever started.
+     */
+    static void startVersionDetection();
+
+    /**
+     * @brief Cached installed-miner version parsed by startVersionDetection().
+     * Empty until detection completes (or if no binary/parse failed). Thread-safe.
+     */
+    static std::string installedVersion();
+
 private:
     bool generateConfig(const Config& cfg, const std::string& outPath);
     bool startProcess(const std::string& xmrigPath, const std::string& cfgPath, int threads);