feat(wallet): persist history and surface pending sends

Add an encrypted SQLite transaction history cache with cached tip metadata and
per-address shielded scan progress so startup and full refreshes avoid
re-scanning every z-address while still invalidating on wallet/address/rescan
changes.

Improve wallet history loading by paging transparent transactions, preserving
cached shielded and sent rows, keeping recent/unconfirmed activity visible, and
classifying mining-address receives. Show z_sendmany opid sends immediately in
History and Overview, pin pending rows through refreshes, and apply optimistic
address/balance debits until opids resolve.

Add timestamped RPC console tracing by source/method without logging params or
results, reduce redundant refresh/RPC calls, and cache Explorer recent block
summaries in SQLite.

Expand focused tests for transaction cache encryption, scan-progress
persistence/invalidation, history preservation, operation-status parsing,
pending send visibility, and Explorer/RPC refresh behavior.

src/ui/layout.h

@@ -576,7 +576,7 @@ inline float mainCardTargetH(float formW, float vs) {
     float innerW   = formW - pad * 2;
     float qrColW   = innerW * 0.35f;
     float qrPad    = spacingMd();
-    float maxQrSz  = std::min(qrColW - qrPad * 2, 280.0f * dp);
+    float maxQrSz  = std::min(std::max(0.0f, qrColW - qrPad * 2), 280.0f * dp);
     float qrSize   = std::max(100.0f * dp, maxQrSz);
     float totalQr  = qrSize + qrPad * 2;
     float innerGap = spacingLg();