nwc: fix make_invoice timestamps (ms -> seconds) breaking NWC clients

generate() stores `created` in milliseconds (Date.now()), but the NWC
make_invoice response returned it directly as created_at and computed
expires_at = created_at + expiry. NWC timestamps are Unix SECONDS (NIP-47),
so clients parsed a ~1.78e12 expires_at that overflowed their date types —
e.g. ptcpay's .NET DateTimeOffset, whose max is 253402300799 (issue #84:
"creating lightning invoices via NWC fails ... Valid values are between
-62135596800 and 253402300799"). Convert created to seconds before use.

The other NWC handlers were already correct (lookup_invoice reads seconds
straight from cln; list_transactions divides p.created by 1000). Only
make_invoice leaked milliseconds.

Fixes #84

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

1 files changed, 8 insertions, 5 deletions

diff --git a/lib/nwc.ts b/lib/nwc.ts
index 5677fea3..2213d68a 100644
--- a/lib/nwc.ts
+++ b/lib/nwc.ts
@@ -403,11 +403,14 @@ const handle = (method, params, ev, app, user) =>
         expiry,
       };
 
-      const {
-        hash,
-        created: created_at,
-        paymentHash,
-      } = await generate({ invoice, user });
+      const { hash, created, paymentHash } = await generate({ invoice, user });
+
+      // generate() stores `created` in milliseconds (Date.now()), but NWC
+      // timestamps are Unix SECONDS (NIP-47). Returning ms here produced an
+      // expires_at ~1.78e12 that overflowed clients' date parsers — e.g.
+      // ptcpay's .NET DateTimeOffset (issue #84: "Valid values are between
+      // -62135596800 and 253402300799"). Convert to seconds.
+      const created_at = Math.floor(created / 1000);
 
       return result({
         type: "incoming",