Fix DNS domain name case preservation and DNS 0x20 encoding issues.

Fixed DNS 0x20 encoding bug in worker threads and removed automatic lowercasing in DNS buffer parsing to preserve case from authoritative sources. Implemented case-insensitive lookups for cache and blockchain while ensuring restoration of the original client query case in all response paths instead of returning randomized DNS 0x20 case from upstream servers.

src/dns/protocol.rs

@@ -505,6 +505,23 @@ impl DnsRecord {
         }
     }
 
+    pub fn set_domain(&mut self, new_domain: String) {
+        match self {
+            DnsRecord::A { ref mut domain, .. }
+            | DnsRecord::AAAA { ref mut domain, .. }
+            | DnsRecord::NS { ref mut domain, .. }
+            | DnsRecord::CNAME { ref mut domain, .. }
+            | DnsRecord::SRV { ref mut domain, .. }
+            | DnsRecord::PTR { ref mut domain, .. }
+            | DnsRecord::MX { ref mut domain, .. }
+            | DnsRecord::UNKNOWN { ref mut domain, .. }
+            | DnsRecord::SOA { ref mut domain, .. }
+            | DnsRecord::TXT { ref mut domain, .. }
+            | DnsRecord::TLSA { ref mut domain, .. } => *domain = new_domain,
+            DnsRecord::OPT { .. } => {} // OPT records don't have a domain field
+        }
+    }
+
     pub fn get_data(&self) -> Option<String> {
         match *self {
             DnsRecord::A { ref addr, .. } => Some(addr.to_string()),