feat(merge): run per-address consolidation as a paced background job

"Keep in each address" posted one task that called z_mergetoaddress for
every batch of every address back to back; each call is a whole-wallet
scan under cs_main, and the daemon runs the ops one at a time anyway.
It is now an App-owned services::ConsolidationRun:

- one RPC at a time; the next merge only after the previous batch left the
  queue and a gap as long as the last call took (2-120 s);
- pauses while the node syncs, the wallet is locked, a send of ours is in
  progress, or another wallet scan is running;
- failures classified: nothing that may have queued is ever resent; a
  breaker stops after 3 dead addresses or 3 failed ops in a row;
- each merge is charged to the scan budget; one re-read and one forced
  balance at the end;
- it keeps running when the dialog closes: a status-bar chip, a run view
  with progress, the wait reason and a Stop button.

The "Into one" merge can no longer be confirmed twice while its call is
in flight. fake_dragonxd gains FAKE_SCAN_SECS, FAKE_MERGE_SERIAL and
FAKE_MERGE_FAIL.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app.cpp

@@ -1427,6 +1427,8 @@ void App::update()
     // While the address scan that normally ends the send progress can't run (the background, a catch-up, the
     // connect gate, a retry hold), end it once the operations are done: it keeps the window rendering.
     if (send_progress_active_ && !addressScanCanRunNow()) maybeFinishTransactionSendProgress();
+    // C210: the "Keep in each address" consolidation run, if one is going (paced; one RPC at a time).
+    pumpConsolidation();
 
     // After a bootstrap the preserved wallet.dat has stale spent-state and must be reconciled
     // against the freshly-imported chain, or the first send tries to spend already-spent notes and
@@ -2979,6 +2981,30 @@ void App::renderStatusBar()
         ImGui::TextColored(ImVec4(0.6f, 0.8f, 1.0f, 1.0f), "%s%s", TR("sb_importing_keys"), dotStr);
     }
 
+    // C210: a consolidation run keeps going after its dialog closes. A static chip (no animation, no frames of
+    // its own); clicking it reopens the run view.
+    if (consolidation_.active()) {
+        const services::RunProgress p = consolidation_.progress();
+        const ImVec4 col(0.6f, 0.8f, 1.0f, 1.0f);
+        ImGui::SameLine(0, sbSectionGap);
+        ImGui::TextDisabled("|");
+        ImGui::SameLine(0, sbSeparatorGap);
+        ImGui::BeginGroup();
+        ImGui::PushFont(ui::material::Type().iconSmall());
+        ImGui::TextColored(col, ICON_MD_CALL_MERGE);
+        ImGui::PopFont();
+        ImGui::SameLine(0, sbIconTextGap);
+        ImGui::TextColored(col, TR("merge_run_chip_fmt"), p.batchesSubmitted, std::max(1, p.batchesEstimated));
+        ImGui::EndGroup();
+        if (ImGui::IsItemHovered()) {
+            ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
+            if (!p.stopping) {
+                if (const char* k = services::runWaitKey(p.wait)) ui::material::Tooltip("%s", TR(k));
+            }
+        }
+        if (ImGui::IsItemClicked()) ui::ShieldDialog::showConsolidate();   // reopens the run view
+    }
+
     // Right side: version always at far right, connection status to its left.
     // Compute positions dynamically from actual text widths so they
     // never overlap and always stay within the window at any font scale.