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.cpp

@@ -524,9 +524,16 @@ bool EmbeddedDaemon::start(const std::string& binary_path)
         args.push_back("-wallet=" + wallet_file_);
     }
 
-    // Add wallet-repair flag if requested (one-shot). -zapwallettxes=2 wipes all wallet tx/note
-    // records and rebuilds them from the chain; it implies -rescan, so don't also pass -rescan.
-    if (zap_on_next_start_.exchange(false)) {
+    // Add wallet-repair flag if requested (one-shot). Precedence: salvage > zap > rescan; each implies a
+    // rescan in the daemon, so we don't stack them.
+    if (salvage_on_next_start_.exchange(false)) {
+        // -salvagewallet recovers readable keypairs from a corrupt wallet.dat; the daemon then implies -rescan.
+        DEBUG_LOGF("[INFO] Adding -salvagewallet flag to recover a corrupt wallet\n");
+        args.push_back("-salvagewallet");
+        zap_on_next_start_.store(false);
+        rescan_on_next_start_.store(false);
+    } else if (zap_on_next_start_.exchange(false)) {
+        // -zapwallettxes=2 wipes all wallet tx/note records and rebuilds them from the chain (implies -rescan).
         DEBUG_LOGF("[INFO] Adding -zapwallettxes=2 flag for wallet repair (zap & rebuild)\n");
         args.push_back("-zapwallettxes=2");
         rescan_on_next_start_.store(false);  // implied by zap; avoid redundant -rescan