feat(node): warn when the daemon auto-recovers (salvages) wallet.dat

dragonxd auto-recovers a wallet.dat that fails BDB verification on startup — no
flag needed (CWallet::Verify → CDBEnv::Verify(walletFile, CWalletDB::Recover)):
it moves the original to wallet.<timestamp>.bak, salvages readable keys into a
fresh wallet.dat, and keeps running. The salvage can be incomplete (or the whole
thing a FALSE POSITIVE from stale/cross-platform BDB env state — __db.* / the
database/ dir carried between machines), so the node silently comes up on a
possibly-empty wallet. To the user that reads as fund loss, with no warning.

Detect it and warn loudly instead:
- daemon/daemon_startup_diagnosis.h: pure walletAutoRecovered() (the salvage /
  "Original wallet.dat saved as wallet.<ts>.bak" markers) + newestWalletSalvageBak()
  (picks the wallet.<unixtime>.bak the recovery just made).
- onConnected() scans the node's captured output once per session; on a match it
  shows a warning dialog + notification: the ORIGINAL is safe in wallet.<ts>.bak,
  the shown balance may be incomplete, and here are the exact steps to restore it
  (rename the .bak back + delete the stale database/ + __db.* env). One-click
  "Open data folder" jumps straight there. Full-node only; lite-safe.

Deliberately does NOT auto-swap the wallet files (untested per-platform file
manipulation on a real wallet is not worth the risk) — it informs + guides.

Adds walletAutoRecovered / newestWalletSalvageBak coverage to
testBlockDbOutputDiagnosis. Suite green (1/1).

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

src/util/i18n.cpp

@@ -1193,6 +1193,14 @@ void I18n::loadBuiltinEnglish()
         strings_["block_db_reindex_notify"] = "The node can't read its block database (often after a daemon update). Rebuild it to restore your balance — see the prompt, or Settings › Node.";
         strings_["block_db_reindex_started"] = "Rebuilding the block database from your blocks — this can take a while.";
 
+        // Wallet auto-recovery warning (the node moved wallet.dat aside and loaded a salvaged copy).
+        strings_["wallet_recovered_title"] = "Your wallet was auto-recovered";
+        strings_["wallet_recovered_warn"] = "The node moved your wallet aside and loaded a salvaged copy.";
+        strings_["wallet_recovered_body"] = "On startup the node decided your wallet.dat looked damaged and recovered it automatically. Your ORIGINAL wallet was NOT deleted — it was renamed to \"wallet.<numbers>.bak\" in your data folder, and a salvaged copy is loaded now.\n\nThe salvaged copy may be incomplete, so the balance shown here could be wrong — don't treat it as final.\n\nThis is often a false alarm caused by leftover database files (e.g. after moving the wallet between machines). To restore your original: quit the wallet, then in the data folder rename the current wallet.dat aside, rename \"wallet.<numbers>.bak\" back to \"wallet.dat\", delete the \"database\" folder and any \"__db.*\" files, and reopen.";
+        strings_["wallet_recovered_open_folder"] = "Open data folder";
+        strings_["wallet_recovered_dismiss"] = "Keep salvaged copy";
+        strings_["wallet_recovered_notify"] = "The node recovered your wallet and moved the original to a .bak — your shown balance may be incomplete. See the prompt to restore it.";
+
         // Receive Tab
         strings_["receiving_addresses"] = "Your Receiving Addresses";
         strings_["new_z_shielded"] = "New z-Address (Shielded)";