fix(mining): remediate mining-tab audit (22 findings) — crash-safety, async control, validation, math

Fixes all 22 confirmed findings from the mining-tab audit (10 Medium, 12 Low; 0 Critical/High),
adversarially reviewed (6 follow-ups found + fixed, incl. the review-caught idle-auto-start bypass
and a wrong benchmark-restore condition).

Crash-safety & lifecycle:
- M-04: join a stale/finished monitor thread in XmrigManager::start() and ~XmrigManager so an xmrig
  crash-then-restart (or quit) no longer std::terminate()s the wallet.
- L-03/L-10: surface an unexpected miner exit once and clear the stale running flag.

UI never blocks (M-03/L-06/L-08/L-09/L-13): pool start/stop now run on a dedicated serialized FIFO
mining-control thread (joined before teardown), so the ~13 call sites don't block the render thread on
stop()'s SIGTERM->SIGKILL->join; the spawn result marshals back to the UI.

Miner-process / pool trust boundary:
- M-01: validate the payout address (util::isValidRecipientAddress) at EVERY start path — the UI gate
  AND App::startPoolMining() (idle auto-start / thread scaling) — so a stale/wrong-chain address can't
  silently lose rewards.
- M-09: SSRF guard skips the background pool-stats GET for loopback/private/link-local/single-label hosts.
- M-02/L-02: cap the pool-stats + xmrig-API HTTP response bodies.
- L-01: write the xmrig config 0600 at creation (POSIX open with mode) — no world/group-readable window.
- M-10: reject shell-metacharacter binary paths before the version popen (excluding '()' so Program Files
  (x86) still works).

Solo mining: M-06/M-08 clamp thread count to [1, cores] at the setgenerate/xmrig boundary; M-07 notify +
don't lie on stop failure.

Correctness: L-05 block-time constant 75->150s (chainparams); M-05 discloses pool-mode "Est. Daily" as a
rough solo-equivalent; L-04/L-11/L-12 benchmark lifecycle (cancel on nav-away / mode-switch with restore,
skip rebalance mid-benchmark); L-07 honor cancel mid-extract in both the xmrig and daemon updaters.

Two new i18n keys back-filled across all 8 languages; CJK subset font rebuilt for the new glyphs.
Verified across full-node, lite, and Windows builds; tests pass.

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

src/app.h

@@ -14,6 +14,7 @@
 #include <unordered_map>
 #include <unordered_set>
 #include <deque>
+#include <condition_variable>
 #include <nlohmann/json_fwd.hpp>
 #include "data/transaction_history_cache.h"
 #include "data/address_book.h"
@@ -855,6 +856,16 @@ private:
     bool lite_startup_lock_checked_ = false;
     std::unique_ptr<daemon::DaemonController> daemon_controller_;
     std::unique_ptr<daemon::XmrigManager> xmrig_manager_;
+    // Serialized async mining-control queue: xmrig start/stop (SIGTERM->SIGKILL->join, up to ~3s) run on
+    // this dedicated FIFO thread instead of the render thread, so the UI never blocks and stop/start
+    // ordering is preserved across the ~13 call sites. (M-03/L-06/L-08/L-09/L-13)
+    std::thread mining_ctl_thread_;
+    std::mutex mining_ctl_mutex_;
+    std::condition_variable mining_ctl_cv_;
+    std::deque<std::function<void()>> mining_ctl_queue_;
+    bool mining_ctl_stop_ = false;
+    void postMiningControl(std::function<void()> job);  // enqueue a blocking xmrig op onto the FIFO thread
+    void stopMiningControlThread();                     // signal + join the control thread (shutdown)
     // Auto-balance runtime state (pool mining, full-node only). The service fetches
     // pool hashrates off-thread; the RNG drives the weighted-random pick.
     util::PoolStatsService pool_stats_service_;