fix(resilience,perf): gate send on a known tip, surface dropped/stale txs, advance cached confs, memoize explorer

Backlog mediums (display/gating/caching only — no send/sweep/encrypt call or args changed):

Resilience:
- Gate Send/Review on a KNOWN peer-derived tip (SyncInfo::sendTipReady): a fresh reconnect or peerless node
  has tip_known=false, so its local height isn't a trustworthy network tip — sending is disabled with a
  clear tooltip until it is. Lite is exempt (its own sync gate). The z_sendmany call is untouched.
- History now shows "Dropped" for a conflicted tx (confirmations < 0) and "Expired?" for one unconfirmed
  > 1h, instead of "Pending" forever (new TransactionInfo::isConflicted/isStalePending; the tab inlines the
  check on its DisplayTx fields).
- A cached z_viewtransaction row's confirmations now advance by the blocks mined since it was sampled
  (observed_height), instead of freezing at the cached value; never goes backwards; pending (0) isn't
  extrapolated.

Performance:
- Explorer block list uses loadRangeCached() (memoized on the cache revision) instead of loadRange(), so it
  only hits SQLite after the cache changes, not every frame.

Tests: testResilienceMediums (tip gate, confirmations-advance, dropped/stale predicates) + loadRangeCached
memoization in testExplorerBlockCache (isolated on its own cache). Held: Overview/Balance per-frame list
cache, peers clippers, off-thread tx-history cache load (larger refactors).

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

src/services/network_refresh_service.cpp

@@ -1056,8 +1056,13 @@ NetworkRefreshService::TransactionViewCacheEntry NetworkRefreshService::parseVie
 
 void NetworkRefreshService::appendViewTransactionOutputs(std::vector<TransactionInfo>& transactions,
                                                          const std::string& txid,
-                                                         const TransactionViewCacheEntry& entry)
+                                                         const TransactionViewCacheEntry& entry,
+                                                         int currentHeight)
 {
+    // A mined entry's confirmations grow by one per block since it was sampled; never go backwards.
+    int entryConfirmations = entry.confirmations;
+    if (entry.confirmations >= 1 && entry.observed_height >= 0 && currentHeight > entry.observed_height)
+        entryConfirmations += currentHeight - entry.observed_height;
     for (const auto& out : entry.outgoing_outputs) {
         bool alreadyTracked = false;
         for (const auto& existing : transactions) {
@@ -1089,7 +1094,7 @@ void NetworkRefreshService::appendViewTransactionOutputs(std::vector<Transaction
             }
         }
         if (!foundExistingMetadata) {
-            info.confirmations = entry.confirmations;
+            info.confirmations = entryConfirmations;
             info.timestamp = entry.timestamp;
         }
         transactions.push_back(std::move(info));
@@ -1476,7 +1481,7 @@ NetworkRefreshService::TransactionRefreshResult NetworkRefreshService::collectTr
         auto cached = snapshot.viewTxCache.find(txid);
         if (cached != snapshot.viewTxCache.end()) {
             if (!trackedSend || !cached->second.outgoing_outputs.empty()) {
-                appendViewTransactionOutputs(result.transactions, txid, cached->second);
+                appendViewTransactionOutputs(result.transactions, txid, cached->second, currentBlockHeight);
                 // NB: do NOT extract chat metadata from our OWN outgoing memos here — ingest marks
                 // everything Incoming, so that duplicates every sent message as a phantom "from peer"
                 // entry. Genuine incoming comes from the z_listreceivedbyaddress path; our sends are
@@ -1509,6 +1514,7 @@ NetworkRefreshService::TransactionRefreshResult NetworkRefreshService::collectTr
             }
 
             auto entry = parseViewTransactionCacheEntry(viewTransaction);
+            entry.observed_height = currentBlockHeight;   // confirmations below are sampled at this tip
             const bool storedRow = rowBacklog.count(txid) > 0;
             if (storedRow && entry.timestamp == 0) {
                 const auto settled = settledStoredMeta.find(txid);