feat(wallet): detect a corrupt target wallet on switch + offer -salvagewallet repair

When a switch fails, the failure modal now distinguishes a CORRUPT target wallet
from other failures and offers a one-click repair:
- The switch worker watermarks the node's captured console output before the
  start and, if the node dies in init, scans this start's output for a corruption
  signature ("Failed to rename … .bak" / "salvage failed" / "wallet.dat corrupt" /
  "Error loading wallet") → sets switch_wallet_corrupt_.
- The Failed modal then shows an accurate "this wallet appears corrupt" message
  (instead of the generic "Couldn't open that wallet") plus a "Try to repair
  (salvage)" button that retries the switch with the target node started under
  -salvagewallet (recovers readable keypairs; implies -rescan).
- EmbeddedDaemon::setSalvageOnNextStart (one-shot, precedence salvage > zap >
  rescan) + controller forwarder; switchToWallet gains a salvage arg.

Salvage operates only on the corrupt target (never the good wallet, no fund
movement). Adversarially verified: output isolation, one-shot lifecycle, state
handling, re-entrancy, no success-path regression.

i18n (EN + 8 languages) + 2 new CJK glyphs baked into the subset font.

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

src/daemon/embedded_daemon.h

@@ -201,6 +201,11 @@ public:
     void setZapOnNextStart(bool v) { zap_on_next_start_ = v; }
     bool zapOnNextStart() const { return zap_on_next_start_.load(); }
 
+    // -salvagewallet: attempt to recover keys from a corrupt wallet.dat on startup (implies -rescan in
+    // the daemon). One-shot, consumed on the next start. Used to repair a wallet a switch flagged corrupt.
+    void setSalvageOnNextStart(bool v) { salvage_on_next_start_ = v; }
+    bool salvageOnNextStart() const { return salvage_on_next_start_.load(); }
+
     /**
      * @brief One-shot isolated-datadir override for the NEXT start(): run the daemon against a
      *        different datadir (with its own DRAGONX.conf) plus the given extra args. Used by the
@@ -274,6 +279,7 @@ private:
     std::atomic<int> crash_count_{0};  // consecutive crash counter
     std::atomic<bool> rescan_on_next_start_{false};  // -rescan flag for next start
     std::atomic<bool> zap_on_next_start_{false};     // -zapwallettxes=2 flag for next start
+    std::atomic<bool> salvage_on_next_start_{false}; // -salvagewallet flag for next start
     std::string override_datadir_;                   // one-shot: -datadir for the next start
     std::vector<std::string> override_extra_args_;   // one-shot: extra args for the next start
     bool skip_port_check_ = false;                   // isolated instance on a non-default port