Add global music player, invoicing/payment system, account subpages, mail account admin, and the qualityiron.vegas Jet 2.0 port

Jet interpreter (Tag.cpp, __call.cpp, __imap*.cpp/h, __smtpsend.cpp/h,
__imapemptyfolder.cpp/h - new): assorted parser/tag fixes found across
this work - a stray literal-tag-in-comment and backslash-quote parser
corruption class, a dangling-pointer fix, a __call.cpp fd leak, IMAP
folder-management tags, multi-account/per-host IMAP support, and a
smtpsend Message-ID fix.

barant.com site (jetc/barant-site/):
- A site-wide persistent music player (header band, playlist/queue,
  stereo FFT EQ, session-persisted state) fed by new library/
  ianslibrary/music song-list subpages.
- /account split into info/phones/invoices subpages; a full invoicing
  and Square payment system (create/edit/copy/pay/email invoice);
  admin invoice management and mail-account management subpages.
- /services split into overview/hosting/siptrunking/documents
  subpages, retiring the old standalone pages.
- SIPPHONE.tag: a Jet 2.0 WebRTC softphone tag.
- main.css/spa.js/email.js: the SPA loading indicator, the music
  player band styling, and assorted fixes accumulated alongside this
  work.

qualityiron-site/: the qualityiron.vegas job/contractor/customer/
document management app, ported from its original Jet 1.4 codebase to
Jet 2.0 as barant.coms APIServers second multi-tenant site.

wcwc/wcwc.jet: the WCWC site Jet source (wcwc.jtc build output not
included).

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

__imap.h

@@ -63,6 +63,15 @@ namespace jet {
       coreutils::MString setFlag(const std::string &folder, uint32_t uid, const std::string &flag, bool add);
       coreutils::MString deleteMessage(const std::string &folder, uint32_t uid);
       coreutils::MString moveMessage(const std::string &folder, uint32_t uid, const std::string &destFolder);
+      // Permanently empties an entire folder - every message, not one at
+      // a time. "1:*" is IMAP's standard UID-range syntax for "every UID
+      // in the selected mailbox" (well-defined and a no-op, not an error,
+      // on an already-empty folder - verified directly against
+      // BARANTMail rather than assumed from the RFC), so this is a
+      // single mark-all-deleted STORE plus one EXPUNGE, not a loop over
+      // deleteMessage() - the whole point is one IMAP round trip instead
+      // of one per message.
+      coreutils::MString emptyFolder(const std::string &folder);
       coreutils::MString folderCounts();
 
       coreutils::MString sessionId;