fix(ecash): stop Minibits LN-address claims from being silently lost

A Minibits /claim response consumes the payment server-side the instant
it's returned — it can never be re-fetched. claim_and_redeem previously
decrypted/redeemed each claim inline and just warn!-logged any failure,
so a mint-unreachable blip, a stale cached server key, or an operator
who'd edited their accepted-mints list to drop the default mint (via
streaming.configure-mints) could make a real payment vanish with
nothing but a log line to show for it — claimed_count/received_sats
still came back as a clean 0, identical to "nothing arrived."

Now: every fetched claim is persisted to MinibitsState.pending_claims
before decrypt/redeem is attempted, survives failures across polls
instead of being dropped, and claim_and_redeem no longer bails out on a
fetch error without first retrying whatever was already pending.
ensure_mint_accepted self-heals the accepted-mints allow-list so the
Minibits mint (the address is inherently backed by it) can't be
excluded out from under a claim. ClaimOutcome gains failed_count,
threaded through wallet.ecash-lnaddress-claim and shown in
ReceiveBitcoinModal so a stuck claim is visible instead of silent.

Also fixes the server_nostur_pubkey field-name typo (no live state to
migrate — this feature hasn't shipped yet).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EawZPP9iidXj6Tvg3EpG3a

core/archipelago/src/api/rpc/wallet.rs

@@ -432,11 +432,16 @@ impl RpcHandler {
     /// `wallet.ecash-lnaddress-claim` — redeem any Lightning payments that
     /// arrived on the node's Minibits address as ecash. Returns the sats swept in
     /// (0 when nothing was waiting), so the UI can refresh its balance.
+    /// `failed_count` is non-zero when a payment was fetched (and so already
+    /// consumed server-side) but couldn't be redeemed yet — it stays queued
+    /// and is retried automatically, but the UI should tell the operator
+    /// rather than let it be a silent, unbounded wait.
     pub(super) async fn handle_wallet_ecash_lnaddress_claim(&self) -> Result<serde_json::Value> {
         let outcome = crate::wallet::minibits::claim_and_redeem(&self.config.data_dir).await?;
         Ok(serde_json::json!({
             "claimed_count": outcome.claimed_count,
             "received_sats": outcome.received_sats,
+            "failed_count": outcome.failed_count,
         }))
     }