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>

res/lang/de.json

@@ -1294,6 +1294,8 @@
     "sweep_to": "Gefegt an:",
     "sweep_toggle": "In meine Wallet fegen (Schlüssel nicht behalten)",
     "sweep_tx": "Transaktion:",
+    "switch_corrupt_body": "Diese Wallet scheint beschädigt zu sein – der Knoten konnte sie nicht öffnen. Aus einem Backup wiederherstellen, neu erstellen oder eine Reparatur versuchen.",
+    "switch_corrupt_repair": "Reparatur versuchen (Salvage)",
     "switch_progress_background": "Im Hintergrund fortsetzen",
     "switch_progress_default_wallet": "Standard-Wallet",
     "switch_progress_elapsed": "Vergangen",