docs: the panel as it is in 2.0

Stage 3, step 3. Written by Sonnet from the code and the plan, checked
by Opus.

  - guide.md: a section on the panel - menu, paths, the roles global and
    domain with outbound and inbound assigned separately -, Overview and
    Health, Queue and System log, Account and Server > Settings, the
    domain page / Domain settings / application form, Help as a page of
    topics. The DMARC report address is one of three choices set in
    Domain settings. The Spam filter box, the two INBOUND_ANTISPAM_*
    variables the panel reads, and the filter's socket on Health.
    Sessions; backup and export encrypted unless the box is unticked;
    1.x data is not restored into 2.0.
  - architecture.md: Panel HTTP surface rewritten from web.go (routes,
    the /server/ guard, per-object checks, <page>/fragment, one layout,
    typed page data, the kit and its guards, CSP and htmx); Persistence
    gains the database - one baseline, a 1.x file refused, the tables as
    they are.
  - security.md: roles and what each reaches, as built; sessions by user
    id and what ends them; state-changing requests; errors shown to
    users; the 2.0 review; two accepted risks from it - a delegated
    inbound upstream may be any host and port, and Account's profile is
    saved without the password.
  - CHANGELOG: Removed opens with "2.0 starts from an empty data
    directory"; entries that describe the user-default report address
    say they were replaced before release; the filter's socket.
  - roadmap.md: two review follow-up rows struck as retired by the
    redesign (.pair / .split, the two back links); password-reset notes
    that changing the account e-mail must then ask for the password.
    Progress 25/27.
  - development.md: the component kit and its guards; README and
    product.md: wording.

Left as they are
  - The third follow-up row the plan expected to strike - initShowWhen
    is not re-run after an htmx swap - still holds: no polled fragment
    carries such a control today, so nothing breaks, but the redesign did
    not retire it.
  - guide.md embeds no screenshots, so none needed retaking.
  - README and guide still name image 1.9.5 - the version cut.
  - plans/preflight.md and plans/inbound-antispam-panel.md use pre-2.0
    paths; roadmap's template-data-typing is largely done by the
    redesign.

  go test -count=1 ./cmd/panel (env-doc tables): ok

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

README.md

@@ -26,9 +26,9 @@ send log and DNS checks in the panel, encrypted backups.
 - Outbound SMTP (465/smtps; optional 587 submission) with per-domain DKIM signing
 - Optional inbound relay on port 25 (backup-MX / forwarder; off by default)
 - Optional DMARC aggregate report ingest on port 25 (off by default)
-- In-panel Help drawer and `/help` page for Status and domain controls
+- In-panel Help: a page of topics, opened from the `?` in the head of a box
 - Per-application client IP allow-list for SMTP AUTH (optional)
-- Web panel — domains, applications, deliveries, mail queue, system log, backup
+- Web panel grouped by mail direction — Overview, Outbound (domains, log, queue, DMARC reports), Inbound, Server (health, system log, backup, users, settings)
 - Multi-domain relay — each SASL application is bound to one sending domain
 - DNS status checks (PTR, SPF, DKIM, DMARC) with in-panel re-check
 - Two-level rate limiting — IP backstop (Postfix), per-domain ceilings, and trusted-IP app overrides