release: 1.9.2: Review pass: port-25 milters, DMARC validation, rate-limit fix

Review pass over `1.4.0`…`1.9.1`: port 25 no longer shares the submission milter chain, DMARC reports are validated before they are stored, and the auto rate limit is correct for a non-default level-1 window. Schema migration `0010` (index only). Upgrading is a tag bump.
Added:
  - SQLite migration `0010_send_log_app_login_index.sql` —
  - DMARC aggregate reports are accepted as **zip** as well as gzip or plain XML
  - e2e: `checkPort25ConfigCombinations` regenerates the Postfix configuration
Changed:
  - README hero line and a **Positioning** block in `docs/product.md` record the
Fixed:
  - The setup account's password is hashed at bcrypt cost `12` like every other
  - Login/setup rate limiter: protecting blocked buckets from eviction is now
  - `postqueue -p` output is bounded to 4 MiB (the timeout alone left the size of
  - [schema-migrations.md](docs/schema-migrations.md): the schema section was
  - postqueue reader is now time-bounded: `postqueue -p` runs under a 5-second
  … (11 more in CHANGELOG)
Changed:
  - [roadmap.md](docs/roadmap.md) now carries everything the 2026-08-19 code
  - Extracted `internal/configsafe` — the empty-value and forbidden-character
  - Build, deploy and migration comments no longer cite the archived
  - Dropped the `parseDomainRateLimitForm` / `parseAppRateLimitForm` pass-through
  - Extracted shared helpers: `internal/atomicfile` (atomic temp-write+rename) and
  … (7 more in CHANGELOG)
Removed:
  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs
  - Plan documents for already-shipped features: `domain-stats-auto-ratelimit`,

Full detail: CHANGELOG.md (1.9.2).

internal/store/domains.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"modernc.org/sqlite"
@@ -182,3 +183,17 @@ func (s *Store) UpdateDomainDMARCRua(id int64, rua sql.NullString) error {
 	}
 	return nil
 }
+
+// DomainExists reports whether a sending domain with this name is configured.
+// Used by the DMARC ingest path to refuse reports for domains this relay does
+// not send for (security.md: report XML is attacker-supplied input).
+func (s *Store) DomainExists(name string) (bool, error) {
+	var n int
+	err := s.db.QueryRow(
+		"SELECT COUNT(*) FROM domains WHERE name = ? COLLATE NOCASE", strings.TrimSpace(name),
+	).Scan(&n)
+	if err != nil {
+		return false, fmt.Errorf("domain exists %q: %w", name, err)
+	}
+	return n > 0, nil
+}