panel-notifications: Account, Server > Settings, Server > Health, help; e2e

The pages of the mockups accepted in 87fa0a4, built from the kit's partials
(written by a Sonnet agent into the working tree, reviewed here):

- Account: "Send me notifications" in the Profile form, saved with the
  profile; an unticked box is off.
- Server > Settings: the instance switch (box 03), and box 04 Notification
  mail with the DKIM and SPF records of the server's own name, drawn with the
  record partial of a domain's DNS page and checked in DNS. Sending rate
  limits are box 02 in the left column. A record that is not in place is
  tagged as a warning, not a failure: notifications are sent without it.
- Server > Health: card 06 Notification mail with the state of each record
  and a link to Settings, beside Configuration (07); part of the polled
  fragment; Re-check DNS forces it too. Overview does not run this check.
- help.go: the Notifications topic and the clauses in Settings and Your
  account, word for word with help.html.

If the server's key cannot be read the pages still render: the DKIM record
is left out and SPF is shown unchecked.

e2e: the administrator gets a mailbox behind the sink and the server's DKIM
record from Settings is published; the level-2 refusal of the next step must
then arrive as a notification from postmaster@mail.e2e.test, signed as that
name with the key Settings shows, and must not be a row of the Outbound log.
The rotation step now waits for Postfix to be running: it follows a step that
restarts the container, and logrotate's `postfix reload` failed in between.

On the test server, for this tree: go vet clean, go test ./... 23 packages
ok, make e2e ok (147 s); the notification reached the sink 28 s after the
refusal.

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

internal/web/view/templates/account.html

@@ -14,6 +14,8 @@
       <div class="field"><label class="label" for="username">Username</label><div class="control has-icons-left"><input class="input" id="username" name="username" value="{{.Username}}" autocomplete="username" autocapitalize="none" spellcheck="false" required><span class="icon is-left"><i class="ti ti-user"></i></span></div></div>
       <div class="field"><label class="label" for="email">E-mail</label><div class="control has-icons-left"><input class="input" id="email" name="email" type="email" value="{{.Email}}" autocomplete="email" autocapitalize="none" spellcheck="false"><span class="icon is-left"><i class="ti ti-mail"></i></span></div>
         <p class="help">Your own address. A domain's report address can be filled with it from Domain settings.</p></div>
+      <div class="field"><label class="checkbox"><input type="checkbox" name="notify"{{if .Notify}} checked{{end}}> Send me notifications</label>
+        <p class="help">To this address, when something needs you: a DNS record of a domain stops matching, a rate limit refuses mail, the TLS certificate is about to expire, a message has waited in the queue for three days. <a href="/help#notifications">What is sent and when</a></p></div>
       <button type="submit" class="button is-primary">Save profile</button>
     </form>
     {{template "body_close"}}