Add real IMAP4rev1/POP3 implementations, DKIM/DMARC/SPF, SpamAssassin delivery hook

IMAP (RFC 3501): LOGIN through UID, previously all stubs except
CAPABILITY/LOGOUT/a partial APPEND. Multi-folder support with per-folder
UID/flag indexing (new MailFolder class, backed by .uidvalidity/.uidnext/
.imapindex sidecar files), ENVELOPE support (new MessageHeaders class:
header parsing, address-list parsing, IMAP quoting), and shared
cursor-based argument parsing (new IMAPArgs class: sequence sets, flag
lists, dates, folder-name normalization, and path-traversal protection
via isValidFolderName - a bare ".." folder name would otherwise resolve
into a sibling user's mailbox directory).

POP3 (RFC 1939): USER through QUIT, previously only CAPA. Added UIDL.
POP3 handlers use cursor-based parsing throughout rather than indexed
access - ZString's copy constructor doesn't copy its `list` field, and
POP3's dispatch passes the request by value, so indexed access into a
copy was silently reading nothing.

SMTP: DMARC evaluation added to the DATA-terminator path (DKIM
verification + alignment/policy, Authentication-Results header,
conditional rejection matching RFC 7489 6.3's p=reject + sampled pct=).
AUTH LOGIN now handles RFC 4954's optional inline initial response
(e.g. Python smtplib's "AUTH LOGIN <base64>" in one line) instead of
only the exact three-line form. Outbound relay now forces IPv4
(AF_INET) instead of AF_UNSPEC - this server's IPv4 has a correct PTR
record and SPF coverage, its IPv6 doesn't, and Gmail was rejecting
outbound mail with 550 5.7.25 as a result.

Delivery pipeline: local delivery now runs the message through
SpamAssassin (new SpamAssassinFilter class, speaking spamd's PROCESS
protocol directly over a raw socket - fails open/delivers unscanned if
spamd is unreachable) instead of a plain hardlink, since scanning can
tag/modify content.

BARANTMailConfig: extracted config loading into its own class.

compile: (see individual file changes - build script adjustments to
match the above).

Deliberately excluded from this commit: barantmail.log/
barantmail-service.log (operational logs, not source - barantmail.log
in particular was the runaway 55GB/12.9GB file from a busy-loop bug
fixed separately in ServerCore) and barantmail.cfg (this server's own
live deployment config, matching how APIServer's equivalent
config also stays untracked).

BARANTMailConfig.cpp

@@ -0,0 +1,95 @@
+#include "BARANTMailConfig.h"
+#include "Exception.h"
+#include "JFile.h"
+
+namespace mail {
+
+   BARANTMailConfig::BARANTMailConfig(const std::string &path) {
+      file = new coreutils::JFile(coreutils::ZString(path.c_str(), path.length()));
+
+      if (!file->exists("hostName"))
+         throw coreutils::Exception("BARANTMailConfig: \"hostName\" is missing from " + path);
+      if (!file->exists("mailPath"))
+         throw coreutils::Exception("BARANTMailConfig: \"mailPath\" is missing from " + path);
+      if (!file->exists("smtp.port"))
+         throw coreutils::Exception("BARANTMailConfig: \"smtp.port\" is missing from " + path);
+
+      bool needsTls = file->exists("smtpTLS.port") || file->exists("imap.port") || file->exists("pop3.port");
+      if (needsTls) {
+         if (!file->exists("tls.certificate") || !file->exists("tls.key"))
+            throw coreutils::Exception(
+               "BARANTMailConfig: smtpTLS/imap/pop3 is configured but \"tls.certificate\"/\"tls.key\" "
+               "is missing from " + path);
+         certPath = file->getString("tls.certificate");
+         keyPath = file->getString("tls.key");
+         tlsInfo.certificate = certPath.c_str();
+         tlsInfo.key = keyPath.c_str();
+         if (file->exists("tls.caCertificate")) {
+            caPath = file->getString("tls.caCertificate");
+            tlsInfo.cACertificate = caPath.c_str();
+         }
+         hasTls = true;
+      }
+   }
+
+   BARANTMailConfig::~BARANTMailConfig() {
+      delete file;
+   }
+
+   std::string BARANTMailConfig::getHostName() {
+      return file->getString("hostName");
+   }
+
+   std::string BARANTMailConfig::getMailPath() {
+      return file->getString("mailPath");
+   }
+
+   int BARANTMailConfig::getSmtpPort() {
+      return (int)file->getInt("smtp.port");
+   }
+
+   bool BARANTMailConfig::hasSmtpTLS() {
+      return file->exists("smtpTLS.port");
+   }
+
+   int BARANTMailConfig::getSmtpTLSPort() {
+      return (int)file->getInt("smtpTLS.port");
+   }
+
+   bool BARANTMailConfig::hasImap() {
+      return file->exists("imap.port");
+   }
+
+   int BARANTMailConfig::getImapPort() {
+      return (int)file->getInt("imap.port");
+   }
+
+   bool BARANTMailConfig::hasPop3() {
+      return file->exists("pop3.port");
+   }
+
+   int BARANTMailConfig::getPop3Port() {
+      return (int)file->getInt("pop3.port");
+   }
+
+   core::TLSInfo *BARANTMailConfig::getTlsInfo() {
+      return hasTls ? &tlsInfo : NULL;
+   }
+
+   bool BARANTMailConfig::hasDkim() {
+      return file->exists("dkim.domain") && file->exists("dkim.selector") && file->exists("dkim.privateKey");
+   }
+
+   std::string BARANTMailConfig::getDkimDomain() {
+      return file->getString("dkim.domain");
+   }
+
+   std::string BARANTMailConfig::getDkimSelector() {
+      return file->getString("dkim.selector");
+   }
+
+   std::string BARANTMailConfig::getDkimPrivateKeyPath() {
+      return file->getString("dkim.privateKey");
+   }
+
+}