panel-redesign: Help with seventeen topics; every box links to its own

Follows the design commit before it. Written by Sonnet, reviewed by
Opus.

  - view/help.go, templates/help.html: the mockup's topics, texts, ids
    and menu. The page shows the groups the reader's menu shows:
    Overview and Server for the global role, Outbound and Inbound by
    reach (Inbound only with the feature on), Account for everyone;
    boxes are numbered as shown.
  - Box.Help set on the boxes the mockups mark; the inbound MX box has
    its link again.
  - TestEveryHelpLinkLandsOnATopic also fails on a topic that no page
    links to, unless it is listed as menu-only (account) - and on a
    stale exception.

Known until the change that follows: the dns, dmarc and account topics
describe the three-choice report address, which the code does not have
yet; Account's DMARC box still links to #dns.

Not verified by running: three sentences rest on Postfix behaviour
(delivery is deferred when a required TLS session cannot be made; a
milter with default_action=tempfail answers 4xx; with "any recipient"
an address the upstream refuses comes back as a bounce).

Evidence
  - docs/assets/panel-redesign/evidence/help.png (1440x3600) and
    in-domain.png: headless Edge, real templates served locally with
    their fixtures - NOT from the container.
  - go test -count=1 ./internal/web/... ./cmd/panel: ok (six packages).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/view/templates/help.html

@@ -1,7 +1,7 @@
-{{/* Help (mockup help.html): one topic per heading, stacked in two boxes, with a
-     menu that jumps to each. A box on another page links to the topic that
-     explains it by the topic's id (Box.Help). Overview is absent for a viewer
-     who does not see the pages it explains. */}}
+{{/* Help (mockup help.html): one topic per heading, stacked in one box per section
+     of the panel, with a menu that jumps to each. A box on another page links to
+     the topic that explains it by the topic's id (Box.Help). A section is absent
+     for a viewer who cannot open its pages, and so is its part of the menu. */}}
 {{define "content"}}
 {{template "page_head" .Head}}
 
@@ -10,16 +10,12 @@
 {{template "side_menu" .Menu}}
   </div>
   <div class="column is-9">
-{{if .ShowOverview}}
-{{template "box_open" .Overview}}
-{{range .OverviewTopics}}{{template "help_topic" .}}
+{{range .Groups}}
+{{template "box_open" .Box}}
+{{range .Topics}}{{template "help_topic" .}}
 {{end}}
 {{template "box_close"}}
 {{end}}
-{{template "box_open" .Outbound}}
-{{range .OutboundTopics}}{{template "help_topic" .}}
-{{end}}
-{{template "box_close"}}
   </div>
 </div>
 {{end}}