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, 12 insertions, 0 deletions

diff --git a/tools/sp-indexer.js b/tools/sp-indexer.js
index 12f76f7..d573ab9 100644
--- a/tools/sp-indexer.js
+++ b/tools/sp-indexer.js
@@ -109,6 +109,18 @@ Bun.serve({
       const b = blocks.get(Number(m[1]));
       return json(b ? b.items.map((i) => i.tweak) : []);
     }
+    // All SP-eligible tx items from height `from` to the tip, in one response —
+    // each tagged with its height. Lets a client scan a range without one fetch
+    // per block. (Regtest-scale; mainnet would page or use BIP-158 filters.)
+    if ((m = p.match(/^\/scan\/(\d+)$/))) {
+      const from = Number(m[1]);
+      const items = [];
+      for (let h = from; h <= indexed; h++) {
+        const b = blocks.get(h);
+        if (b) for (const it of b.items) items.push({ height: h, ...it });
+      }
+      return json({ tip: indexed, items });
+    }
     return json({ error: 'not found' }, 404);
   },
 });