port 25 ends DATA only at CRLF.CRLF: smtpd_forbid_bare_newline=normalize (port25-bare-newline)

Postfix 3.7.11 leaves its 2023 SMTP-smuggling defence off (default "no"
before 3.9, src/smtpd/smtpd.c:807), and the inbound relay's smtp/inet
listener did not turn it on: a "." line ended by a bare LF ended DATA and
what followed was read as the next transaction. The listener now sets
normalize (bare_lf_mask_table, smtpd.c:1656; the DATA loop drops such a
"." line, 3649-3652), the setting Postfix recommends and 3.9's default.
The submission ports keep the default (own-mta-builds, section 5).

Tests: e2e inbound_bare_newline_is_one_message sends the smuggling
sequence over raw SMTP (net/smtp's DotWriter would rewrite the bare LF)
and finds one message at the upstream with the smuggled part inside;
port25 config check asserts the parameter on smtp/inet. On the server:
make e2e exit 0 (511 s), go vet + go test 27 packages ok.

Docs: CHANGELOG [Unreleased] Security, security.md, architecture.md,
guide.md; roadmap: port25-bare-newline, base-trixie and
panel-dkim-signing agreed by the owner in this order.

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

docs/guide.md

@@ -1010,7 +1010,11 @@ SelfPost never stores the message locally.
 container. Until then there is no inbound-relay `smtp inet` listener, no
 *Inbound* group in the menu, and `/inbound/…` is 404. (Port 25 can still
 listen when only `DMARC_REPORTS_ENABLE=true` — see [DMARC
-reports](#dmarc-reports).) Outbound 465/587 is unchanged.
+reports](#dmarc-reports).) Outbound 465/587 is unchanged. Port 25 ends a
+message only at the standard `<CR><LF>.<CR><LF>` (the SMTP-smuggling
+defence, since `2.6.1`); a sending server that ends DATA with a bare
+newline waits for a reply that does not come, and there is no allow-list
+for such a sender.
 
 **Panel** (`/inbound/domains`): the global role adds and deletes domains. On a
 domain's page, set the upstream host/port and TLS to that hop (opportunistic /