chore(ci): add govulncheck, staticcheck, go vet, gofumpt gates

* Add lint/format checks to the Gitea release workflow and Makefile
  (targets: vet, fmt, fmt-check, staticcheck, govulncheck, check)
* Switch .golangci.json formatter from gofmt to gofumpt (extra.group-params)
* Bump golang.org/x/text 0.37.0 -> 0.39.0 for GO-2026-5970; re-vendor
* Fix staticcheck S1011 in pkg/diff; drop unused pgsql writer helpers
* Fix gocritic unnamedResult (pkg/diff) and rangeValCopy (pkg/pgsql)
* Apply gofumpt + goimports formatting across the tree

tests/integration/orm_roundtrip_test.go

@@ -5,6 +5,9 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers"
 	bunreader "git.warky.dev/wdevs/relspecgo/pkg/readers/bun"
@@ -14,8 +17,6 @@ import (
 	bunwriter "git.warky.dev/wdevs/relspecgo/pkg/writers/bun"
 	gormwriter "git.warky.dev/wdevs/relspecgo/pkg/writers/gorm"
 	yamlwriter "git.warky.dev/wdevs/relspecgo/pkg/writers/yaml"
-	"github.com/stretchr/testify/require"
-	"gopkg.in/yaml.v3"
 )
 
 // ComparisonResults holds the results of database comparison
@@ -38,7 +39,7 @@ func countDatabaseStats(db *models.Database) (tables, indexes, constraints int)
 			constraints += len(table.Constraints)
 		}
 	}
-	return
+	return tables, indexes, constraints
 }
 
 // compareDatabases performs comprehensive comparison between two databases

tests/integration/roundtrip_test.go

@@ -9,6 +9,10 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/jackc/pgx/v5"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers"
 	dctxreader "git.warky.dev/wdevs/relspecgo/pkg/readers/dctx"
@@ -17,9 +21,6 @@ import (
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 	jsonwriter "git.warky.dev/wdevs/relspecgo/pkg/writers/json"
 	pgsqlwriter "git.warky.dev/wdevs/relspecgo/pkg/writers/pgsql"
-	"github.com/jackc/pgx/v5"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 // getTestConnectionString returns a PostgreSQL connection string from environment