fix: port-25 milter chain, DMARC report validation, auto rate-limit window

Review pass over the 1.4.0-1.9.1 work.

Port 25 no longer inherits main.cf's submission milter chain: smtpd_milters
is always overridden on smtp/inet, to the antispam milter or to nothing.
Without that, OpenDKIM (strict, tempfail) gated relayed mail during a signing
outage, and the journal-milter filed inbound mail into the outbound send log
under the sender's domain -- so Deliveries showed other people's mail and a
forged From: consumed that domain's level-2 budget. architecture.md already
described the intended behaviour; the code now matches.

DMARC reports are checked before they are stored: the policy domain must be a
configured sending domain, and must match the +tag of a per-domain hosted
address. The rua address form is predictable, so anyone able to reach it could
file reports under any domain and evict genuine ones through the retention cap.
Zip attachments are now decompressed as well as gzip.

The auto level-2 ceiling is scaled to the level-1 window before the multiplier
is applied; any window other than 3600s shifted the allowance by window/3600.

Migration 0010 indexes send_log(app_login, created_at) -- both the per-MAIL
FROM rate-limit count and the per-application statistics were scanning the
created_at range.

e2e now regenerates the Postfix config in-container for all four port-25 flag
combinations and requires postfix check to pass; the 1.9.1 crash-loop shipped
in 1.4.0 and survived three releases because only the flags-off path was
exercised.

Migration 0009 stays as shipped -- its conversion branch only fires for a
database carrying application-scope allowed_ips from before 1.9.0. The schema
reference notes that the old list was permissive and the new column is
restrictive; the guide documents the allow-list as a sending control on a
fail-open path, not an authentication boundary.

Also: gofmt across cmd/ and internal/, unused duplicate validators dropped from
internal/web/validate, export no longer swallows store errors.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/architecture.md

@@ -73,7 +73,11 @@ smtp/inet` removes Debian's stock smtpd). Outbound delivery still uses the
 - **587/submission** — only when `SUBMISSION_ENABLE=true`; STARTTLS with
   `smtpd_tls_security_level=encrypt`.
 - **25/smtp inet** — when `INBOUND_RELAY_ENABLE=true` and/or
-  `DMARC_REPORTS_ENABLE=true`. No SASL, no OpenDKIM, no journal-milter.
+  `DMARC_REPORTS_ENABLE=true`. No SASL, no OpenDKIM, no journal-milter —
+  `smtpd_milters` is always overridden on this service (to the antispam milter
+  or to nothing), because main.cf's submission chain would otherwise let a
+  signing outage defer relayed mail and would file inbound mail into the
+  outbound send log under the sender's domain.
   **Inbound relay** (`INBOUND_RELAY_ENABLE=true`): accepts only
   `relay_domains` + `relay_recipient_maps` (`reject_unauth_destination`,
   `reject_unlisted_recipient`). Maps under `/data/postfix/` (`relay_domains`,
@@ -117,9 +121,12 @@ One process, four roles:
 2. **journal-milter** — unix socket `JOURNAL_MILTER_SOCKET`; records From/To/
    Subject/SASL user at DATA; enforces level-2 rate limits; **fail-open**
    (`default_action=accept`) so milter failure does not stop mail. Domain
-   ceilings apply to every client IP; an application ceiling with trusted IPs
-   raises the limit for those IPs only and skips the domain check (guide § Rate
-   limiting). The level-2 count is the stored send-log rows plus the messages
+   ceilings apply to every client IP; an application ceiling **overrides** the
+   domain one for that login, higher or lower (guide § Rate limiting). Since
+   1.9.0 the client IP allow-list is a separate, restrictive control on the
+   application (`applications.auth_ip_restrict`), checked here at `MAIL FROM`
+   and fail-open like the rest of this milter — not an authentication
+   boundary. The level-2 count is the stored send-log rows plus the messages
    this process has admitted but not yet written (`internal/milter/inflight.go`),
    so concurrent sessions cannot each spend the same last slot; a reservation
    is released at end-of-message, on ABORT, or after a 10-minute TTL.