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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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

@@ -41,3 +41,34 @@ func TestParseQueueIDsOnAnEmptyQueue(t *testing.T) {
 		t.Errorf("got %v, want no ids", ids)
 	}
 }
+
+// The queue listing is held in memory and rendered into a page, so a very large
+// queue must not size the panel's allocation: the writer keeps the cap and
+// reports the rest as dropped, while still accepting every write so postqueue
+// itself is never cut short.
+func TestLimitWriterCapsOutput(t *testing.T) {
+	w := &limitWriter{remaining: 8}
+	n, err := w.Write([]byte("12345"))
+	if n != 5 || err != nil {
+		t.Fatalf("first write = %d, %v", n, err)
+	}
+	if w.truncated {
+		t.Fatal("truncated before the cap was reached")
+	}
+	n, err = w.Write([]byte("67890"))
+	if n != 5 || err != nil {
+		t.Fatalf("second write = %d, %v", n, err)
+	}
+	if !w.truncated {
+		t.Fatal("write past the cap was not recorded as truncated")
+	}
+	if got := w.buf.String(); got != "12345678" {
+		t.Fatalf("kept %q, want the first 8 bytes", got)
+	}
+	if n, err := w.Write([]byte("more")); n != 4 || err != nil {
+		t.Fatalf("write after the cap = %d, %v (must still accept)", n, err)
+	}
+	if got := w.buf.String(); got != "12345678" {
+		t.Fatalf("buffer grew past the cap: %q", got)
+	}
+}