Cap refresh chain lifetime via RefreshChainAbsoluteTTL

Sessions had an absolute cap (created_at + SessionAbsoluteTTL) but the
JWT path only had per-token TTL on the refresh row, letting a
well-behaved client refresh indefinitely. Add chain_started_at to
authkit_tokens, copy it forward on every rotation, and reject in
RefreshJWT when now > chainStartedAt + RefreshChainAbsoluteTTL.
Default 30d, mirroring SessionAbsoluteTTL.

Schema, verifier, queries, model, and integration test updated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

testdb_test.go

@@ -52,17 +52,18 @@ func freshAuth(t *testing.T) *Auth {
 		DB:     db,
 		Hasher: hasher.NewArgon2id(hasher.DefaultArgon2idParams(), nil),
 	}, Config{
-		JWTSecret:           []byte("integration-secret-thirty-two!!!"),
-		JWTIssuer:           "authkit-int",
-		AccessTokenTTL:      2 * time.Minute,
-		RefreshTokenTTL:     time.Hour,
-		SessionIdleTTL:      time.Hour,
-		SessionAbsoluteTTL:  24 * time.Hour,
-		EmailVerifyTTL:      time.Hour,
-		PasswordResetTTL:    time.Hour,
-		MagicLinkTTL:        time.Minute,
-		EmailOTPTTL:         time.Minute,
-		EmailOTPMaxAttempts: 3,
+		JWTSecret:               []byte("integration-secret-thirty-two!!!"),
+		JWTIssuer:               "authkit-int",
+		AccessTokenTTL:          2 * time.Minute,
+		RefreshTokenTTL:         48 * time.Hour,
+		RefreshChainAbsoluteTTL: 24 * time.Hour,
+		SessionIdleTTL:          time.Hour,
+		SessionAbsoluteTTL:      24 * time.Hour,
+		EmailVerifyTTL:          time.Hour,
+		PasswordResetTTL:        time.Hour,
+		MagicLinkTTL:            time.Minute,
+		EmailOTPTTL:             time.Minute,
+		EmailOTPMaxAttempts:     3,
 	})
 	if err != nil {
 		t.Fatalf("authkit.New: %v", err)