Wire silent-payment receiving into the wallet (scan + balance + UI)

wallet.js: scanSilentPayments() pulls the indexer's /scan range, matches outputs
on-device, and verifies each is unspent via the chain backend; spUtxos + balance
are tracked in their own bucket (one-time taproot keys), persisted in the cache.
silentPaymentsAvailable()/spBalance() expose state.

app.js: the Receive tab shows the reusable sp address (QR + copy), a 'Scan for
silent payments' button, and the found amount; Settings gains a per-network SP
indexer picker (under Data source) with custom/self-host support.

sp-indexer.js: added /scan/{from} so a client fetches a whole range in one
request instead of one fetch per block.

Receiving verified end-to-end on regtest (scan finds the output, 49,999,800 sat
confirmed). Spending SP outputs is the remaining piece.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/i18n.js b/src/i18n.js
index 2fe840d..5f029a3 100644
--- a/src/i18n.js
+++ b/src/i18n.js
@@ -301,6 +301,15 @@ const STR = {
     electrumUrl: 'Electrum server (wss://)',
     electrumUrlHint: 'A WebSocket Electrum server, e.g. wss://your-node:50004',
     silentPaymentNote: 'Silent payment',
+    spReceiveTitle: 'Silent payment address',
+    spReceiveDesc: 'A reusable address that leaks nothing on-chain — each sender derives a unique, unlinkable output. Scanning finds payments on-device using the indexer set under Data source.',
+    spScan: 'Scan for silent payments',
+    spScanning: 'Scanning…',
+    spReceived: 'Found {n} silent payment output(s): {amount}',
+    spIndexerTitle: 'Silent payment indexer',
+    spIndexerDesc: 'Where to scan for received silent payments. It only serves public tweak data — your scan key stays on-device — but a public one can see which blocks hold your outputs, so self-host for full privacy.',
+    spIndexerUrl: 'Indexer URL',
+    spIndexerHint: 'A BIP-352 tweak indexer (e.g. your own).',
     deviceSync: 'Device sync',
     deviceSyncDesc: 'Keep this wallet in sync across your devices by storing an encrypted copy on a Nostr relay — only a device with your seed can read it. Turn it off to keep everything on this device.',
     syncAcross: 'Sync across devices',