fix(discovery): add SO_REUSEPORT for multiple mDNS listeners

capsule-core/src/discovery.zig

@@ -30,6 +30,7 @@ pub const DiscoveryService = struct {
 
         // 2. Allow port reuse (standard for mDNS)
         try posix.setsockopt(fd, posix.SOL.SOCKET, posix.SO.REUSEADDR, &std.mem.toBytes(@as(i32, 1)));
+        try posix.setsockopt(fd, posix.SOL.SOCKET, posix.SO.REUSEPORT, &std.mem.toBytes(@as(i32, 1)));
 
         // 3. Bind to all interfaces on mDNS port
         const bind_addr = try net.Address.parseIp("0.0.0.0", MULTICAST_PORT);