fix(core): refresh transaction history on the Mining tab

The Mining tab shows earnings derived from transaction history, but it
was not treated as a wallet-data page, so newly mined or paid-out
earnings did not appear until the user left the tab and came back. A
coinbase row also changes category in place (immature becomes generate
at maturity, or orphan on a reorg), and the Recent merge kept both the
old and the new row, double-counting the earnings.

- The Mining tab now gets the cheap between-blocks Recent poll: one
  listtransactions per new block, bounded by the 15 s transaction-age
  timer, once history has loaded. It never runs a full routine scan and
  never pre-empts an owed dirty cycle; tracked sends still take their
  normal cycle on any page.
- The shielded-payout probe runs only while the pool miner is running,
  since pool payouts are shielded receives while a solo miner's earnings
  are transparent coinbase rows.
- The Recent merge drops the previous row of the other coinbase category
  when a coinbase transitions, so maturing or reorged rewards are no
  longer counted twice. A non-coinbase row sharing the txid is left
  alone.

Behaviour change: mining earnings update on the Mining tab per block
instead of only on tab re-entry, and maturing or reorged coinbase rows
no longer double-count.

Tests: the per-block poll gate (one poll per block, due only after
history loads, held while dirty or addresses are dirty), the Mining-page
cycle shaping, and the coinbase transition merge for immature to
generate, generate to orphan, and a shared-txid non-coinbase row.

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

src/services/history_scan_policy.h

@@ -148,5 +148,23 @@ struct TxCycleInputs {
 // Light cycle, so it can't loop them at one tip.
 TxCycle decideTxCycle(const TxCycleInputs& in);
 
+// The Mining tab shows history-derived earnings but is not a wallet-data page: it gets the cheap between-blocks
+// poll (recent listtransactions rows) and nothing routine. Explicit work (first load, dirty, new addresses) and
+// tracked sends still go through the normal cycles on any page.
+TxCycleInputs shapeTxCycleForMiningPage(TxCycleInputs in);
+
+struct MiningTxPollInputs {
+    int  tip = 0;                 // current chain height
+    int  lastPolledTip = -1;      // the tip the last Mining poll was dispatched at (-1 = none)
+    bool txAgeDue = false;        // RefreshTimer::TxAge due (15 s since the last Recent poll / full cycle)
+    bool historyLoaded = false;   // last_tx_block_height_ >= 0
+    bool dirty = false;           // transactions_dirty_
+    bool addressesDirty = false;  // addresses_dirty_
+};
+// One poll per new block (confirmation counts and new coinbase rows only change with a block), after the history
+// has loaded, never while a dirty cycle is already owed. Unlike the wallet pages, an EMPTY history may poll (a fresh
+// miner's first block must appear).
+bool miningTxPollDue(const MiningTxPollInputs& in);
+
 }  // namespace services
 }  // namespace dragonx