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/schema-migrations.md

@@ -18,13 +18,14 @@ Documentation.
 
 | Field | Value |
 |---|---|
-| Chain head | `user_version = 9` |
-| Files | `0001_init.sql` … `0009_application_auth_ips.sql` (9 files) |
+| Chain head | `user_version = 10` |
+| Files | `0001_init.sql` … `0010_send_log_app_login_index.sql` (10 files) |
 | Database file | `/data/selfpost.db` (bind mount) |
 | Compatibility | 1.x MINOR releases must boot a `1.0.0` data directory |
 
-Last updated with release **1.9.0** (`0009_application_auth_ips`); **1.9.1**
-had no schema change.
+Last updated in **[Unreleased]** (`0010_send_log_app_login_index`); **1.9.1**
+had no schema change. The release column below records the cut a migration
+shipped in — fill `0010`'s in at the next version cut.
 
 ---
 
@@ -42,6 +43,7 @@ had no schema change.
 0002_sessions.sql          → user_version 2
 …
 0009_application_auth_ips.sql → user_version 9
+0010_send_log_app_login_index.sql → user_version 10
 ```
 
 **Implication:** never delete, rename, or reorder migration files while 1.x must
@@ -63,6 +65,7 @@ replace the embedded set (see [Planned 2.x squash](#planned-2x-squash)).
 | 7 | `0007_rate_limit_auto.sql` | 1.6.0 | DDL | `rate_limits.mode`, `auto_multiplier`, `auto_updated_at` |
 | 8 | `0008_dmarc_reports.sql` | 1.7.0 | DDL | `dmarc_reports`, `dmarc_report_records` |
 | 9 | `0009_application_auth_ips.sql` | 1.9.0 | DDL + data | `applications.auth_ip_restrict`, `auth_allowed_ips`; move legacy app `rate_limits.allowed_ips` into auth columns; clear those IPs on rate limits |
+| 10 | `0010_send_log_app_login_index.sql` | Unreleased | DDL | `idx_send_log_app_login_created_at` — app-scoped rate-limit counts and per-application send statistics were scanning the `created_at` range |
 
 **Kind:** *DDL* — schema only; *data* — `INSERT`/`UPDATE` that must stay correct
 for operators upgrading from older 1.x images.
@@ -117,11 +120,17 @@ code. A 2.x baseline should define `users` directly and omit `admin`.
 
 ### Application trusted IPs (0009)
 
-Before 1.9.0, client IP restriction for an application lived in
-`rate_limits.allowed_ips` (`scope = application`). Migration 0009 copies non-empty
-values into `applications.auth_allowed_ips`, sets `auth_ip_restrict = 1`, and
-clears `rate_limits.allowed_ips` for application scope. Level-2 limits no longer
-carry IP bindings; auth and rate limiting are separate concerns.
+Before 1.9.0, client IPs for an application lived in `rate_limits.allowed_ips`
+(`scope = application`). Migration 0009 copies non-empty values into
+`applications.auth_allowed_ips`, sets `auth_ip_restrict = 1`, and clears
+`rate_limits.allowed_ips` for application scope. Level-2 limits no longer carry
+IP bindings; auth and rate limiting are separate concerns.
+
+Note that the two columns do not mean the same thing: the old list was
+*permissive* (those IPs got the application ceiling, every other IP fell back
+to the domain limit), the new one is *restrictive* (every IP not on the list is
+refused for that application). The conversion branch only fires for a database
+that carried application-scope `allowed_ips` from before 1.9.0.
 
 ### Profile DMARC email (0004 → 0005)