Add IMAP webmail tag, admin/opensource subpage tiers, store/cart, htmleditor, uploads

New __imap*/__smtpsend/__eval Jet tags give templates real IMAP
(list/message/flag/delete/move/search/folders/accounts) and SMTP-send
capability, backing the new /email webmail client (email.jet/
email.menu, assets/images/email.js + newemail.js) and its
mainpagetemplate.jet-based page shell. Most of this tag family's
source was already being built into the live site (Tag.cpp already
registered __imap/__imaplist/__imapmessage/__imapflag/__imapdelete/
__eval) but had never actually been committed; this also registers
and commits the remaining five (__imapmove/__imapfolders/
__imapsearch/__smtpsend/__imapaccounts).

admin.page/admin.menu gain a real subpage tier (admin-email,
admin-newemail, admin-invoices, admin-products, admin-users) replacing
several previously top-level pages, mirrored by a similar
opensource.page subpage tier (opensource-overview/asm1802/barantmail/
jet/serverframework/synthmax) - old top-level pages retired via git
rename (asm1802.page, jet.page, serverframework.page,
admin_invoices.page); barantmail.page is dropped outright, folded into
opensource-barantmail.subpage.

New storefront (store.page, store-createstore.subpage,
barantstore.page) and cart flow (cart.jet, updatecartqty.proc,
removecartitem.proc, editproduct.page/selectproduct.proc/
update_product.proc for inventory maintenance against the barant
database).

New document upload/download manager (documents.jet, documents_api.jet,
documents_upload.proc, documents_delete.proc,
assets/images/documents.js + documents-page.js) with a persistent
floating panel, and a rich-text page editor (htmleditor.jet/.page,
createhtmleditor.proc, savehtmleditor.proc, assets/images/htmleditor.js
+ its icon/logo assets).

SESSIONCTL.tag: login now redirects back to the originally-requested
page instead of always landing on /account ($[start:0] vs $[start]
variable-name mismatch).

main.css/menu.bar/invoices.menu/jet_overview.section/login.menu:
styling and navigation updates for the above; new site assets (fonts,
images, audio) referenced by them.

jetc/build-assets.sh, list_jet_files.sh, lowercase_jet.py,
strip_fragments.py: small dev tooling used while building the above.

__smtpsend.h

@@ -0,0 +1,69 @@
+#ifndef ____smtpsend_h__
+# define ____smtpsend_h__
+
+# include "Tag.h"
+# include "ZString.h"
+# include "MString.h"
+# include <openssl/ssl.h>
+# include <string>
+
+namespace jet {
+
+   ///
+   /// <smtpsend config="./email.cfg" user="..." password="..."
+   ///           to="..." subject="..." html="...">
+   ///
+   /// One-shot authenticated SMTP submission to BARANTMAIL's own
+   /// implicit-TLS submission port (config key "smtpPort" - matches
+   /// barantmail.cfg's smtpTLS.port, :465, the same implicit-TLS style
+   /// as IMAP's :993 - no STARTTLS negotiation). Connects, TLS-
+   /// handshakes, AUTH LOGIN with the SAME mailbox credentials already
+   /// used by <imap> (so the message goes out authenticated as the
+   /// actual connected mailbox, not the site's own transactional-mail
+   /// identity - see barant.tag's separate <email> tag for that), then
+   /// MAIL FROM/RCPT TO/DATAs a freshly-built RFC 5322 message
+   /// (Date/From/To/Subject/MIME headers, HTML body), then QUITs. The
+   /// authenticated user IS the From address - SMTP submission
+   /// requires MAIL FROM to match the authenticated identity anyway, so
+   /// there's no separate "from" keyword.
+   ///
+   /// No connection pooling, unlike __imap - composing mail is rare
+   /// enough that a fresh connect/auth/send/close per message is fine.
+   ///
+   /// Throws coreutils::Exception (401 for a bad login, 502 for any
+   /// other connect/protocol/rejected-recipient failure) on any
+   /// failure - same convention as __imap.
+   ///
+   class __smtpsend : public Tag {
+
+    public:
+      __smtpsend(coreutils::ZString &in, coreutils::MString &parentOut, Global &global, Tag *parent, Tag *local);
+
+    private:
+      SSL_CTX *ctx = nullptr;
+      SSL *ssl = nullptr;
+      int fd = -1;
+      std::string recvBuffer;
+      size_t recvPos = 0;
+
+      void sendLine(const std::string &line);
+      char readByte();
+      std::string readLine();
+      // Reads one (possibly multi-line, "250-text"/"250 text"
+      // continuation-marked) SMTP reply and returns its 3-digit code;
+      // throws if the code's first digit doesn't match expectedCode's.
+      int readReply(int expectedCode);
+
+      void closeConnection();
+
+      static std::string base64Encode(const std::string &s);
+      static std::string rfc2822Date();
+      // Builds the full RFC 5322 message (headers + dot-stuffed body)
+      // handed to SMTP's DATA command.
+      static std::string buildMessage(const std::string &from, const std::string &to,
+                                       const std::string &subject, const std::string &html);
+   };
+
+}
+
+#endif