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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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

@@ -1,47 +1,14 @@
 package postfix
 
 import (
-	"fmt"
 	"os"
-	"path/filepath"
+
+	"github.com/mixeme/selfpost/internal/atomicfile"
 )
 
 // writeFileAtomic writes data to path via a temp file in the same directory
 // followed by a rename, so a concurrent Postfix reload only ever sees the
-// complete old or new map, never a partial write (security.md). It mirrors the
-// same primitive used for the OpenDKIM tables.
+// complete old or new map, never a partial write (security.md).
 func writeFileAtomic(path string, data []byte, perm os.FileMode) error {
-	dir := filepath.Dir(path)
-	tmp, err := os.CreateTemp(dir, ".tmp-*")
-	if err != nil {
-		return fmt.Errorf("create temp in %s: %w", dir, err)
-	}
-	tmpName := tmp.Name()
-	cleanup := true
-	defer func() {
-		if cleanup {
-			_ = os.Remove(tmpName)
-		}
-	}()
-
-	if _, err := tmp.Write(data); err != nil {
-		tmp.Close()
-		return fmt.Errorf("write temp %s: %w", tmpName, err)
-	}
-	if err := tmp.Chmod(perm); err != nil {
-		tmp.Close()
-		return fmt.Errorf("chmod temp %s: %w", tmpName, err)
-	}
-	if err := tmp.Sync(); err != nil {
-		tmp.Close()
-		return fmt.Errorf("sync temp %s: %w", tmpName, err)
-	}
-	if err := tmp.Close(); err != nil {
-		return fmt.Errorf("close temp %s: %w", tmpName, err)
-	}
-	if err := os.Rename(tmpName, path); err != nil {
-		return fmt.Errorf("rename %s -> %s: %w", tmpName, path, err)
-	}
-	cleanup = false
-	return nil
+	return atomicfile.Write(path, data, perm)
 }