feat(wallet): clickable onchain card opens transaction history

Tapping the Bitcoin card on the wallet screen now navigates to a new
OnchainTransactionsScreen that lists transactions touching the account's
Taproot address, mirroring the NWC transactions view.

- OnchainBackend gains getTxsForAddress(address, afterTxid) returning
  BitcoinAddressTx rows (netValueSats, confirmations, blockHeight,
  blockTime, counterparty addresses). EsploraBackend implements it via
  GET /address/{addr}/txs and /address/{addr}/txs/chain/{last_seen}
  for pagination; CachingOnchainBackend passes through.
- OnchainTransactionsViewModel loads the address from the account
  signer + LocalCache.onchainBackend, paginates, and for each chain
  row scans LocalCache for an OnchainZapEvent with a matching txid so
  the UI can render the Nostr counterparty (sender pubkey for
  incoming, p-tagged recipient for outgoing).
- ALL / ZAPS / NON-ZAPS filter chips reuse the existing
  TransactionFilter enum. Mempool rows are flagged "Pending" in
  bitcoin-orange.

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/onchain/OnchainZapSenderTest.kt

@@ -30,6 +30,7 @@ import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
 import com.vitorpamplona.quartz.nip57Zaps.LnZapPrivateEvent
 import com.vitorpamplona.quartz.nip57Zaps.LnZapRequestEvent
 import com.vitorpamplona.quartz.nipBCOnchainZaps.builder.OnchainZapBuilder
+import com.vitorpamplona.quartz.nipBCOnchainZaps.chain.BitcoinAddressTx
 import com.vitorpamplona.quartz.nipBCOnchainZaps.chain.BitcoinTx
 import com.vitorpamplona.quartz.nipBCOnchainZaps.chain.FeeEstimates
 import com.vitorpamplona.quartz.nipBCOnchainZaps.chain.OnchainBackend
@@ -69,6 +70,11 @@ class OnchainZapSenderTest {
 
         override suspend fun getUtxosForAddress(address: String): List<Utxo> = utxos
 
+        override suspend fun getTxsForAddress(
+            address: String,
+            afterTxid: String?,
+        ): List<BitcoinAddressTx> = emptyList()
+
         override suspend fun broadcast(rawTxHex: String): String {
             if (broadcastFails) throw RuntimeException("relay rejected tx")
             broadcastedHex = rawTxHex