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>

tests/test_phase4.cpp

@@ -6139,6 +6139,23 @@ void testBlockDbOutputDiagnosis()
     EXPECT_FALSE(blockDbOutputLooksBroken("Error loading wallet"));      // wallet corruption → salvage, not reindex
     EXPECT_FALSE(blockDbOutputLooksBroken("Error: Could not find any asmap file!"));
     EXPECT_FALSE(blockDbOutputLooksBroken(""));
+
+    // Wallet auto-recovery detection: the node salvaged wallet.dat (moved the original to a .bak).
+    using dragonx::daemon::walletAutoRecovered;
+    EXPECT_TRUE(walletAutoRecovered(
+        "Warning: wallet.dat corrupt, data salvaged! Original wallet.dat saved as wallet.1786300000.bak in ..."));
+    EXPECT_TRUE(walletAutoRecovered("wallet.dat corrupt, salvage failed"));
+    EXPECT_FALSE(walletAutoRecovered("Loading wallet...\nWallet completed loading\n"));  // normal load
+    EXPECT_FALSE(walletAutoRecovered(": Error loading block database."));                // block-DB abort != salvage
+    EXPECT_FALSE(walletAutoRecovered(""));
+
+    // Newest salvage backup picker (the "wallet.<unixtime>.bak" the recovery just made).
+    using dragonx::daemon::newestWalletSalvageBak;
+    EXPECT_EQ(newestWalletSalvageBak({"wallet.dat", "wallet.1786200000.bak", "wallet.1786300000.bak", "peers.dat"}),
+              std::string("wallet.1786300000.bak"));   // highest timestamp wins
+    EXPECT_EQ(newestWalletSalvageBak({"wallet.dat", "wallet.dat.encrypted.bak", "notes.txt"}),
+              std::string(""));                          // no wallet.<digits>.bak present
+    EXPECT_EQ(newestWalletSalvageBak({}), std::string(""));
 }
 
 // Live probe of a real lite server (env-gated). Validates CONNECT_ONLY latency + IP capture.