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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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

@@ -1,6 +1,7 @@
 package auth
 
 import (
+	"fmt"
 	"testing"
 	"time"
 )
@@ -123,3 +124,53 @@ func TestRateLimiterCapsBucketCount(t *testing.T) {
 		t.Fatalf("bucket count = %d, want at most 3", len(r.buckets))
 	}
 }
+
+// A flood of new addresses must not be able to reset the limiter for an address
+// that is already blocked: below the hard ceiling, blocked buckets survive
+// eviction even though the map is over its soft cap.
+func TestRateLimiterKeepsBlockedBucketsUnderPressure(t *testing.T) {
+	r := newRateLimiter(2, time.Minute)
+	r.maxBuckets = 3
+
+	blocked := []string{"203.0.113.7", "198.51.100.9", "192.0.2.5"}
+	for _, key := range blocked {
+		for i := 0; i < 2; i++ {
+			if !r.Allow(key) {
+				t.Fatalf("%s refused before reaching the limit", key)
+			}
+		}
+		if r.Allow(key) {
+			t.Fatalf("%s was not blocked after 2 attempts", key)
+		}
+	}
+
+	// Fresh addresses arrive and find nothing evictable.
+	for i := 0; i < 10; i++ {
+		r.Allow(fmt.Sprintf("198.51.100.%d", 100+i))
+	}
+
+	for _, key := range blocked {
+		if r.Allow(key) {
+			t.Fatalf("%s lost its block after new addresses arrived", key)
+		}
+	}
+}
+
+// Protecting blocked buckets is bounded: past maxBuckets * blockedBucketCeiling
+// they are evicted too, so an attacker cannot grow the map without limit by
+// burning through source addresses.
+func TestRateLimiterBoundsBlockedBuckets(t *testing.T) {
+	r := newRateLimiter(1, time.Minute)
+	r.maxBuckets = 2
+	hardCap := r.maxBuckets * blockedBucketCeiling
+
+	for i := 0; i < 100; i++ {
+		r.Allow(fmt.Sprintf("192.0.2.%d", i))
+	}
+
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if len(r.buckets) > hardCap {
+		t.Fatalf("bucket count = %d, want at most the hard cap %d", len(r.buckets), hardCap)
+	}
+}