Merge release/custom-0.1.81 into release/custom-0.1.83

- Resolved conflict in .github/workflows/security-scan.yml: use upstream .gosec.json config
- Resolved conflict in deploy/docker-compose.yml: keep Redis, remove PostgreSQL (use external DB)

backend/internal/repository/gateway_cache_integration_test.go

@@ -104,7 +104,6 @@ func (s *GatewayCacheSuite) TestGetSessionAccountID_CorruptedValue() {
 	require.False(s.T(), errors.Is(err, redis.Nil), "expected parsing error, not redis.Nil")
 }
 
-
 func TestGatewayCacheSuite(t *testing.T) {
 	suite.Run(t, new(GatewayCacheSuite))
 }