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

pkg/diff/diff.go

@@ -264,7 +264,7 @@ func compareColumnDetails(source, target *models.Column) map[string]any {
 
 // comparableColumn accepts DBML's compact type/default spelling as well as
 // PostgreSQL's normalized fields (for example varchar(255) vs varchar + 255).
-func comparableColumn(column *models.Column) (string, int, any) {
+func comparableColumn(column *models.Column) (normalizedType string, length int, defaultVal any) {
 	typeName := strings.TrimSpace(column.Type)
 	defaultValue := column.Default
 	lower := strings.ToLower(typeName)
@@ -274,7 +274,7 @@ func comparableColumn(column *models.Column) (string, int, any) {
 		}
 		typeName = strings.TrimSpace(typeName[:i])
 	}
-	length := column.Length
+	length = column.Length
 	if open := strings.LastIndex(typeName, "("); open >= 0 && strings.HasSuffix(typeName, ")") {
 		if parsed, err := strconv.Atoi(strings.TrimSpace(typeName[open+1 : len(typeName)-1])); err == nil && length == 0 {
 			length = parsed
@@ -353,9 +353,7 @@ func compareIndexes(source, target map[string]*models.Index) *IndexDiff {
 	}
 
 	for _, key := range sortedKeys(remainingTarget) {
-		for _, index := range remainingTarget[key] {
-			diff.Extra = append(diff.Extra, index)
-		}
+		diff.Extra = append(diff.Extra, remainingTarget[key]...)
 	}
 	return diff
 }