fix(migrate): require a reorg-safe sweep depth + re-verify before adopt; make the wallet.dat swap crash-safe

Resilience audit, migrate-to-seed (the sweep RPC is byte-identical — see below):
- Adopt was enabled at >= 1 confirmation and never re-read state before stopping the daemon, so a 1-block
  reorg after the swap could un-mine the sweep and strand the funds in the .bak. Adopt now needs a
  reorg-safe depth (>= 10, matching the History "confirmed" threshold), and the button runs
  verifyThenAdoptSeedWallet(): a read-only gettransaction(confs) + z_gettotalbalance minconf 0 (includes
  unconfirmed, fixing the old minconf-1 "no funds" gate) immediately before the daemon stop, refusing while
  syncing or if any read fails. The remainder re-sweep still shows once mined (>=1).
- The wallet.dat swap was rename(legacy->bak) then non-atomic copy(new->wallet.dat): a hard kill left
  wallet.dat missing or half-written. New order: probe the new file is a BDB wallet; stage a size-verified
  copy beside wallet.dat; COPY (never overwrite) the legacy wallet to the timestamped .bak and verify it;
  then ONE atomic fs::rename of the staged file over wallet.dat. At every instant wallet.dat is the whole
  old or whole new wallet, and a verified .bak exists before the replace. On any failure only our scratch
  files are removed; the user's wallet is untouched.

Byte-identical: z_mergetoaddress (beginSweepToSeedWallet, ["ANY_TADDR","ANY_ZADDR"], amounts, fee, recipient,
memo) and beginAdoptSeedWallet's disconnect/vault-removal/stop/rescan/restart logic are unchanged; only the
adopt gating, two new read-only RPCs, presentation, and the file-move safety change. Pure tests:
sweepConfsAreReorgSafe + adoptReverifyPasses.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app.cpp

@@ -5043,7 +5043,7 @@ void App::renderSeedMigrationDialog()
             ImGui::Spacing();
             if (!seed_migration_nofunds_confirmed_) ImGui::BeginDisabled();
             if (ui::material::TactileButton(TR("mig_adopt_now"), ImVec2(190 * dp, 0)))
-                beginAdoptSeedWallet();
+                verifyThenAdoptSeedWallet();   // fresh minconf-0, sync-aware balance check before the swap
             if (!seed_migration_nofunds_confirmed_) ImGui::EndDisabled();
             ImGui::SameLine();
             if (ui::material::TactileButton(TR("refresh"), ImVec2(110 * dp, 0)))
@@ -5107,7 +5107,8 @@ void App::renderSeedMigrationDialog()
 
     case SeedMigrationStep::Confirming: {
         const double dust = DRAGONX_DEFAULT_FEE;  // treat <= one fee as "empty"
-        const bool confirmed = seed_migration_sweep_confs_ >= 1;
+        const bool mined = seed_migration_sweep_confs_ >= 1;   // remainder re-sweep stays offered once mined
+        const bool confirmed = dragonx::sweepConfsAreReorgSafe(seed_migration_sweep_confs_);  // adopt needs reorg-safe depth
         const bool legacyEmpty = seed_migration_legacy_remaining_ >= 0.0 &&
                                  seed_migration_legacy_remaining_ <= dust;
         ImGui::TextWrapped("%s", TR("mig_confirming"));
@@ -5127,8 +5128,8 @@ void App::renderSeedMigrationDialog()
         ImGui::Spacing();
         if (confirmed && legacyEmpty) {
             if (ui::material::TactileButton(TR("mig_adopt"), ImVec2(180 * dp, 0)))
-                beginAdoptSeedWallet();
-        } else if (confirmed && seed_migration_legacy_remaining_ >= 0.0 && !legacyEmpty) {
+                verifyThenAdoptSeedWallet();   // re-reads confs + balance right before the daemon stop
+        } else if (mined && seed_migration_legacy_remaining_ >= 0.0 && !legacyEmpty) {
             // Only claim a remainder once the legacy balance was actually measured; while a sweep is
             // mined but the balance scan is still gated (node syncing), remaining stays at the -1.0
             // sentinel, so fall through to the waiting state rather than offering a sweep on an unknown.
@@ -5152,6 +5153,10 @@ void App::renderSeedMigrationDialog()
                 if (ui::material::TactileButton(TR("cancel"), ImVec2(110 * dp, 0)))
                     seed_migration_confirm_sweep_ = false;
             }
+        } else if (mined && legacyEmpty) {
+            // Mined but not yet reorg-safe deep: say so instead of the misleading "waiting to be mined".
+            char dbuf[200]; snprintf(dbuf, sizeof(dbuf), TR("mig_waiting_depth"), dragonx::kSweepAdoptMinConfs);
+            ImGui::TextWrapped("%s", dbuf);
         } else {
             ImGui::TextColored(kMedium, "%s", TR("mig_waiting_mine"));
         }