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.

jetc/strip_fragments.py

@@ -0,0 +1,96 @@
+"""
+Strips the dead SPA-fragment dual-render wrapper from a barant-site/jet/*.jet
+route file, leaving just the real page content (the former "_full_NAME" tag
+body), unwrapped, with no fragment-flag try/catch, no _frag_NAME tag
+definition, no dispatch <if>, and no dead client-side SPA navigation script.
+
+Structure being removed (present in all 20 files, verified consistent):
+
+  #api GET /NAME
+  <try name="_fragerr">...<catch>...</try><tag name="_frag_NAME">
+      ... fragment-only content, NEVER actually invoked any more since the
+      client-side SPA click handlers were already disabled earlier this
+      session ...
+  </tag><tag name="_full_NAME">
+      ... the REAL page content - full doctype/head/style/body wrapper ...
+      <script>
+      (function() {
+         var FRAGMENT_EXCLUDED = [...];
+         function pageNameFromPath(...) {...}
+         function loadPage(...) {...}
+         // SPA click/popstate interception disabled for now ...
+      })();
+      </script></body></html>
+  </tag><if value1="$[fragflag]" value2="1" type="eq"><_frag_NAME /><else><_full_NAME /></if>
+
+Kept: "#api GET /NAME\n" plus everything between "<tag name=\"_full_NAME\">"
+and its own matching close, MINUS the dead <script> block.
+"""
+import re
+import sys
+
+
+def strip_dead_spa_script(content):
+    pattern = re.compile(
+        r"<script>\s*\(function\(\)\s*\{.*?SPA click/popstate interception disabled.*?\}\)\(\);\s*</script>",
+        re.DOTALL,
+    )
+    new_content, n = pattern.subn("", content, count=1)
+    return new_content, n
+
+
+def strip_fragment_wrapper(content, page_name):
+    lines = content.split("\n", 1)
+    assert lines[0].startswith("#api GET /"), f"unexpected first line: {lines[0]!r}"
+    api_line = lines[0]
+    rest = lines[1] if len(lines) > 1 else ""
+
+    start_marker = (
+        '<try name="_fragerr"><set name="fragflag" expr="$[fragment]" />'
+        '<catch><set name="fragflag" value="" /></try>'
+        f'<tag name="_frag_{page_name}">'
+    )
+    if start_marker not in rest:
+        return None, f"start marker not found"
+    idx = rest.index(start_marker)
+    prefix_extra = rest[:idx]  # should just be leading whitespace/newline, kept as-is
+    rest = rest[idx + len(start_marker):]
+
+    mid_marker = f'</tag><tag name="_full_{page_name}">'
+    if mid_marker not in rest:
+        return None, f"mid marker not found"
+    mid_idx = rest.index(mid_marker)
+    rest = rest[mid_idx + len(mid_marker):]
+
+    end_pattern = re.compile(
+        r'</tag><if value1="\$\[fragflag\]" value2="1" type="eq">'
+        rf'<_frag_{re.escape(page_name)} /><else><_full_{re.escape(page_name)} /></if>\s*$'
+    )
+    m = end_pattern.search(rest)
+    if not m:
+        return None, f"end marker not found"
+    full_content = rest[:m.start()]
+
+    full_content, nscript = strip_dead_spa_script(full_content)
+
+    result = api_line + "\n" + prefix_extra + full_content
+    return result, f"ok (removed {nscript} dead script block(s))"
+
+
+def main():
+    if len(sys.argv) != 4:
+        print("usage: strip_fragments.py <input> <output> <page_name>")
+        sys.exit(1)
+    with open(sys.argv[1], encoding="utf-8", newline="") as f:
+        content = f.read()
+    result, status = strip_fragment_wrapper(content, sys.argv[3])
+    if result is None:
+        print(f"FAILED for {sys.argv[3]}: {status}")
+        sys.exit(1)
+    with open(sys.argv[2], "w", encoding="utf-8", newline="") as f:
+        f.write(result)
+    print(f"{sys.argv[3]}: {status} ({len(content)} -> {len(result)} bytes)")
+
+
+if __name__ == "__main__":
+    main()