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/server.go

@@ -98,11 +98,11 @@ func NewBackup(m Meta, passwordMin int, refusal string) *Backup {
 			Title:  "Backup",
 			Lead:   Plain("Take the whole instance with you, or bring one domain in from another SelfPost. Both files are secrets."),
 		},
-		Full:         Box{No: "01", Title: "Full backup"},
+		Full:         Box{No: "01", Title: "Full backup", Help: topicLink(HelpBackup, "Backups, encryption and restore")},
 		FullAction:   serverBackup,
 		Encrypt:      true,
 		PasswordMin:  passwordMin,
-		Import:       Box{No: "02", Title: "Import a domain", ID: "import"},
+		Import:       Box{No: "02", Title: "Import a domain", ID: "import", Help: topicLink(HelpBackup, "Moving a domain to another instance")},
 		ImportAction: serverBackup + "/import",
 	}
 	if refusal != "" {
@@ -198,7 +198,7 @@ func NewUsers(m Meta, inbound bool, flash string) *Users {
 				Em("global"), " is the whole server, ", Em("domain"), " is ", reach),
 			Actions: []Action{{Label: "Create user", Icon: "ti-user-plus", Href: serverUsers + "/new", Primary: true}},
 		},
-		List:        Box{No: "01", Title: "Panel users"},
+		List:        Box{No: "01", Title: "Panel users", Help: topicLink(HelpUsers, "Roles are a reach, not a rank")},
 		ShowInbound: inbound,
 	}
 	if flash != "" {
@@ -298,7 +298,7 @@ func NewUserForm(m Meta, in UserFormInput) *UserForm {
 		Head:       Head{Crumbs: crumbs, Title: title},
 		CancelHref: serverUsers,
 
-		Account:     Box{No: "01", Title: "Account"},
+		Account:     Box{No: "01", Title: "Account", Help: topicLink(HelpUsers, "Roles and domain assignments")},
 		Username:    in.Username,
 		Email:       in.Email,
 		NewUser:     in.ID == 0,