release: 1.6.0: 30-day send stats and optional auto level-2 rate limits

30-day sending statistics per domain and application, plus optional auto level-2 rate limits derived from average send rate.
Added:
  - Domain page **Sending statistics** card: total messages, peak and average
  - Level-2 rate limit **Manual** / **Auto** mode on domain and application
  - Domain export JSON now includes rate limits (`mode`, `auto_multiplier`,
Changed:
  - Auto mode uses the level-1 window (`RATE_LIMIT_WINDOW_SECONDS`); manual

Full detail: CHANGELOG.md (1.6.0).

internal/store/applications.go

@@ -163,6 +163,25 @@ func (s *Store) GetApplication(id int64) (Application, error) {
 	return a, nil
 }
 
+// GetApplicationByLogin returns one application by its globally unique SASL login.
+func (s *Store) GetApplicationByLogin(login string) (Application, error) {
+	row := s.db.QueryRow(
+		"SELECT id, domain_id, login, address_mode, created_at FROM applications WHERE login = ?", login)
+	a, err := scanApplication(row)
+	if errors.Is(err, sql.ErrNoRows) {
+		return Application{}, ErrApplicationNotFound
+	}
+	if err != nil {
+		return Application{}, err
+	}
+	addrs, err := s.applicationAddresses(a.ID)
+	if err != nil {
+		return Application{}, err
+	}
+	a.Addresses = addrs
+	return a, nil
+}
+
 // ListApplicationsByDomain returns a domain's applications ordered by login,
 // each with its address list populated (product.md).
 func (s *Store) ListApplicationsByDomain(domainID int64) ([]Application, error) {