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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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

@@ -0,0 +1,25 @@
+package configsafe
+
+import "testing"
+
+// The check is the last line of defence before a value reaches a config file,
+// so it must reject both halves of the problem: an empty value that would write
+// a malformed line, and any character from the caller's forbidden set.
+func TestToken(t *testing.T) {
+	if err := Token("domain", "example.com", " \t\r\n,\\"); err != nil {
+		t.Fatalf("clean value rejected: %v", err)
+	}
+	if err := Token("domain", "", " "); err == nil {
+		t.Fatal("empty value accepted")
+	}
+	for _, bad := range []string{"a b", "a\tb", "a\rb", "a\nb", "a,b", "a\\b"} {
+		if err := Token("domain", bad, " \t\r\n,\\"); err == nil {
+			t.Errorf("Token(%q) = nil, want error", bad)
+		}
+	}
+	// A character outside the caller's set is that format's business, not this
+	// function's: a colon is fatal in an OpenDKIM table and fine in a texthash.
+	if err := Token("domain", "a:b", " \t\r\n,\\"); err != nil {
+		t.Errorf("character outside the forbidden set rejected: %v", err)
+	}
+}