Add send-log retention days to panel Settings.

Global administrators can set delivery journal retention (7-365 days) in SQLite;
SEND_LOG_RETENTION_DAYS seeds the initial default and the log-tailer re-reads
the value every prune cycle without a restart.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/store/settings_test.go

@@ -0,0 +1,87 @@
+package store
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestSendLogRetentionDaysSaveLoad(t *testing.T) {
+	st := openTestStore(t)
+
+	if err := st.SetSendLogRetentionDays(45); err != nil {
+		t.Fatalf("SetSendLogRetentionDays: %v", err)
+	}
+	got, err := st.GetSendLogRetentionDays(90)
+	if err != nil {
+		t.Fatalf("GetSendLogRetentionDays: %v", err)
+	}
+	if got != 45 {
+		t.Fatalf("got %d, want 45", got)
+	}
+}
+
+func TestSendLogRetentionDaysRejectsOutOfRange(t *testing.T) {
+	st := openTestStore(t)
+
+	for _, days := range []int{0, 6, 366, -1} {
+		if err := st.SetSendLogRetentionDays(days); err == nil {
+			t.Fatalf("SetSendLogRetentionDays(%d) want error", days)
+		} else if !errors.Is(err, ErrSendLogRetentionDaysOutOfRange) {
+			t.Fatalf("SetSendLogRetentionDays(%d) = %v, want ErrSendLogRetentionDaysOutOfRange", days, err)
+		}
+	}
+}
+
+func TestSendLogRetentionDaysBootstrapFromEnv(t *testing.T) {
+	st := openTestStore(t)
+
+	if err := st.EnsureSendLogRetentionDays(120); err != nil {
+		t.Fatalf("EnsureSendLogRetentionDays: %v", err)
+	}
+	got, err := st.GetSendLogRetentionDays(90)
+	if err != nil {
+		t.Fatalf("GetSendLogRetentionDays: %v", err)
+	}
+	if got != 120 {
+		t.Fatalf("got %d, want 120", got)
+	}
+
+	// Second call is a no-op.
+	if err := st.EnsureSendLogRetentionDays(30); err != nil {
+		t.Fatalf("EnsureSendLogRetentionDays again: %v", err)
+	}
+	got, err = st.GetSendLogRetentionDays(90)
+	if err != nil {
+		t.Fatalf("GetSendLogRetentionDays: %v", err)
+	}
+	if got != 120 {
+		t.Fatalf("after second ensure got %d, want 120", got)
+	}
+}
+
+func TestSendLogRetentionDaysMissingUsesEnvDefault(t *testing.T) {
+	st := openTestStore(t)
+
+	got, err := st.GetSendLogRetentionDays(60)
+	if err != nil {
+		t.Fatalf("GetSendLogRetentionDays: %v", err)
+	}
+	if got != 60 {
+		t.Fatalf("got %d, want 60", got)
+	}
+}
+
+func TestSendLogRetentionDaysInvalidStoredFallsBack(t *testing.T) {
+	st := openTestStore(t)
+
+	if err := st.SetSetting(SendLogRetentionDaysKey, "not-a-number"); err != nil {
+		t.Fatalf("SetSetting: %v", err)
+	}
+	got, err := st.GetSendLogRetentionDays(60)
+	if err != nil {
+		t.Fatalf("GetSendLogRetentionDays: %v", err)
+	}
+	if got != 60 {
+		t.Fatalf("got %d, want env fallback 60", got)
+	}
+}