Fix LNURL comment handling to respect server capabilities (#237)

* fix(zap): only send comment to LNURL callback if server accepts it

The comment in the zap request event (kind 9734 content) is always
included as that's part of the Nostr protocol. However, the LNURL
callback `comment` parameter should only be sent if the server's
`commentAllowed` field is > 0.

Previously, the comment was always sent to the LNURL callback
regardless of the server's comment support, which could cause issues
with servers that don't accept comments.

https://claude.ai/code/session_01KTcAyKHVaqg4QKKXQxUzum

* fix(zap): silently skip comment in LNURL callback if too long

Instead of throwing an error when the comment exceeds the server's
commentAllowed limit, simply don't include it in the LNURL callback.
The comment is still preserved in the zap request event (kind 9734).

https://claude.ai/code/session_01KTcAyKHVaqg4QKKXQxUzum

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/components/ZapWindow.tsx

@@ -352,14 +352,12 @@ export function ZapWindow({
       const comment = serialized.text;
       const emojiTags = serialized.emojiTags;
 
-      // Validate comment length if provided
-      if (comment && lnurlData.commentAllowed) {
-        if (comment.length > lnurlData.commentAllowed) {
-          throw new Error(
-            `Comment too long. Maximum ${lnurlData.commentAllowed} characters.`,
-          );
-        }
-      }
+      // Check if LNURL server accepts comments (commentAllowed > 0)
+      // The comment always goes in the zap request event (kind 9734 content)
+      // But only goes to the LNURL callback if the server accepts it and it fits
+      const commentAllowedLength = lnurlData.commentAllowed ?? 0;
+      const canIncludeCommentInCallback =
+        commentAllowedLength > 0 && comment.length <= commentAllowedLength;
 
       // Step 3: Create and sign zap request event (kind 9734)
       // If zapping anonymously, create a throwaway signer
@@ -385,11 +383,12 @@ export function ZapWindow({
       const serializedZapRequest = serializeZapRequest(zapRequest);
 
       // Step 4: Fetch invoice from LNURL callback
+      // Only include comment if server accepts it and it fits within the limit
       const invoiceResponse = await fetchInvoiceFromCallback(
         lnurlData.callback,
         amountMillisats,
         serializedZapRequest,
-        comment || undefined,
+        canIncludeCommentInCallback ? comment || undefined : undefined,
       );
 
       const invoiceText = invoiceResponse.pr;