Add per-domain DKIM signing, admin console TLS, log rotation, and resolver timeout scoping

- DKIM signing was hardcoded to one domain; now keyed per-domain off
  the sending address, fixing mail for every domain but the original.
- Admin console (port 1027) is now TLS-wrapped instead of plaintext.
- barantmail.log now rotates by size (config-driven) instead of
  growing unbounded (previously hit 23GB).
- ResolverThreadScope.h: a <setenv> scoping fix for name resolution
  inside a <try> block that previously did not survive its own
  container.
- IMAPArgs.cpp: fixed "UID STORE 1:*" wrongly requiring UID 1 to
  exist, which silently made empty-folder operations delete nothing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

SMTPServer.h

@@ -3,6 +3,7 @@
 
 # include <string>
 # include <vector>
+# include <map>
 # include <filesystem>
 # include "EPoll.h"
 # include "TCPServer.h"
@@ -38,18 +39,20 @@ namespace mail {
       // each SMTPServer's own INotify watch is independent, so two
       // watchers on the same directory would each fire inCreate() for
       // every queued message, delivering it twice.
-      // dkimSigner is optional (nullptr = outbound mail goes out
-      // unsigned) and not owned - passed straight through to every
-      // SendMail this instance's inCreate() constructs for outbound
-      // relay.
+      // dkimSigners is optional (nullptr = outbound mail goes out
+      // unsigned for every domain) and not owned - passed straight
+      // through to every SendMail this instance's inCreate() constructs
+      // for outbound relay, which picks the entry matching each
+      // individual message's own sender domain (see SendMail's own doc
+      // comment).
       SMTPServer(core::EPoll &ePoll, std::string hostName, MailFileSystem &mailFileSystem,
                  core::IPAddress ipAddress, core::TLSInfo *tlsInfo, bool watchQueue = true,
-                 DKIMSigner *dkimSigner = nullptr);
+                 std::map<std::string, DKIMSigner*> *dkimSigners = nullptr);
 
       MailFileSystem &mailFileSystem;
       std::string hostName;
       core::EPoll &ePoll;
-      DKIMSigner *dkimSigner;
+      std::map<std::string, DKIMSigner*> *dkimSigners;
 
       // Advertised via EHLO's "250-SIZE <n>" and enforced by __SMTP_DATA
       // while accumulating a message body - RFC 1870. 25MB, matching