fix: exclude sender only for broadcasts, not direct messages

The sender exclusion filter (excludeSenderSessionPubkey) was blocking
delivery of ALL messages from the sender, including direct messages
to other peers. Now only excludes on broadcast (target_spec = '*').

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/broker/src/broker.ts

@@ -1337,7 +1337,7 @@ export async function drainForMember(
           AND delivered_at IS NULL
           AND priority::text IN (${priorityList})
           AND (target_spec = ${memberPubkey} OR target_spec = '*'${sessionPubkey ? sql` OR target_spec = ${sessionPubkey}` : sql``} OR target_spec IN (${groupTargetList}))
-          ${excludeSenderSessionPubkey ? sql`AND (sender_session_pubkey IS NULL OR sender_session_pubkey != ${excludeSenderSessionPubkey})` : sql``}
+          ${excludeSenderSessionPubkey ? sql`AND NOT (target_spec IN ('*') AND sender_session_pubkey = ${excludeSenderSessionPubkey})` : sql``}
         ORDER BY created_at ASC, id ASC
         FOR UPDATE SKIP LOCKED
       )