panel-redesign: Server pages and Help on the kit; the help drawer is gone

Stage 2, step 6. Written by Sonnet, reviewed by Opus.

  - Six pages named after their mockups: system-log, backup, users,
    user, user-delete, help, with typed page data (view/server.go,
    help.go), fixtures and tests. The old templates of the six are gone
    (user_form.html, encrypt_fields.html deleted, the others rewritten)
    and their names are off legacy_pages.txt, which now holds mail_queue
    alone.
  - Help is six help_topic blocks (checks, certificate, rdns, dns, apps,
    limits); a test renders every fixture page and fails on a Help link
    without a topic. The help drawer (help_drawer.html and its includes
    in layout_legacy.html) is removed; its rules in legacy.css go with
    the next step.
  - The user form sets the user's e-mail (plan, Account e-mail): create
    and update, validated, and a changed address resyncs DMARC for a
    user whose default is the account e-mail - through the helper the
    Account profile now shares.
  - Handlers pass typed data; routes, POST targets, field names,
    validation and authorization are unchanged. A test loads the user
    form for four reach combinations and for the only global user, posts
    it back untouched and finds the user unchanged.

Fixed on the way
  - The user delete confirmation said the domains were not affected. A
    domain that follows the user's default report address is left with
    none; the page names those domains now.
  - A refused backup lost the encryption choice and printed a literal
    <code> element in its message.

Differences from the mockups, for the owner:
  - Help has no DMARC and no Inbound topic: its outline fixes two boxes
    of three topics, although other mockups link to #dmarc and #inbound.
    Until the owner decides, Account's Help link goes to #dns and the
    inbound MX box has none;
  - system log: newest line first, as drawn; "refreshes on its own" (5 s
    active, 30 s idle); only status=, warning: and error: lines are
    coloured;
  - backup: the file field is a plain file input; the encryption box is
    ticked, as drawn and as on the domain export, so a plain download
    means unticking it first;
  - users: an E-mail column; the flash does not name the user;
  - user form: no lead; the domain lists are no longer hidden by script
    when Global is chosen (the server ignores them for that role).

Evidence
  - docs/assets/panel-redesign/evidence/system-log.png, backup.png,
    users.png, user.png, user-delete.png, help.png: 1440 px wide,
    headless Edge, real templates served locally with their fixtures -
    NOT from the container (no Docker on this machine).
  - panel/audit.js on the six pages at 1440 and 1280: 720 texts checked,
    problems: [].
  - The system log's polling swap was not exercised in a browser; it
    uses the mechanism of Overview and Health.
  - go test -count=1 ./internal/web/... ./cmd/panel
      ok  internal/web
      ok  internal/web/auth
      ok  internal/web/handlers
      ok  internal/web/validate
      ok  internal/web/view
      ok  cmd/panel

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

CHANGELOG.md

@@ -107,6 +107,12 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
   whether inbound mail is filtered and what happens while the filter is
   down. The filter's address is shown to the global role only. `inbound`,
   `inbound_domain` and `inbound_delete` are off the ratchet.
+- panel-redesign (stage 2): the **Server** pages - System log, Backup,
+  Users, the user form and its delete confirmation - and **Help** are in the
+  new design. Help is a page of topics that the `?` in a box's head opens;
+  the help drawer is gone. The user form sets the user's e-mail. The backup
+  download is encrypted unless the box is unticked. Only the queue page is
+  left on the ratchet.
 
 ### Changed
 
@@ -142,6 +148,9 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
   application forms (the script applied only the first matching rule).
 - The DMARC page of a domain no longer answers 500 once the domain has a
   reported source.
+- The confirmation before deleting a user names the domains that follow
+  that user's default report address and will be left without one; it used
+  to say the domains were not affected.
 
 ### Removed