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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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/configsafe/configsafe.go

@@ -0,0 +1,28 @@
+// Package configsafe holds the defence-in-depth check that every generated
+// configuration file shares: a value about to be written into a table line must
+// be non-empty and must not carry a character that could end the field, end the
+// line, or otherwise change what the file means (security.md).
+//
+// The forbidden set stays with the caller rather than living here, because what
+// breaks a line differs per format — a comma separates values in a Postfix map,
+// a colon separates fields in an OpenDKIM table — and the set belongs next to
+// the writer it protects, where a reviewer of that writer can see it.
+package configsafe
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Token reports whether value is safe to interpolate into a config line. what
+// names the field for the error message ("domain", "login", …) and forbidden
+// lists the characters the format cannot carry.
+func Token(what, value, forbidden string) error {
+	if value == "" {
+		return fmt.Errorf("empty %s", what)
+	}
+	if strings.ContainsAny(value, forbidden) {
+		return fmt.Errorf("unsafe character in %s %q", what, value)
+	}
+	return nil
+}