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/writers/bun/writer.go

@@ -195,7 +195,7 @@ func (w *Writer) writeMultiFile(db *models.Database) error {
 	}
 
 	// Create output directory if it doesn't exist
-	if err := os.MkdirAll(w.options.OutputPath, 0755); err != nil {
+	if err := os.MkdirAll(w.options.OutputPath, 0o755); err != nil {
 		return fmt.Errorf("failed to create output directory: %w", err)
 	}
 
@@ -267,7 +267,7 @@ func (w *Writer) writeMultiFile(db *models.Database) error {
 			filepath := filepath.Join(w.options.OutputPath, filename)
 
 			// Write file
-			if err := os.WriteFile(filepath, []byte(formatted), 0644); err != nil {
+			if err := os.WriteFile(filepath, []byte(formatted), 0o644); err != nil {
 				return fmt.Errorf("failed to write file %s: %w", filename, err)
 			}
 
@@ -471,7 +471,7 @@ func (w *Writer) formatCode(code string) (string, error) {
 // writeOutput writes the content to file or stdout
 func (w *Writer) writeOutput(content string) error {
 	if w.options.OutputPath != "" {
-		return os.WriteFile(w.options.OutputPath, []byte(content), 0644)
+		return os.WriteFile(w.options.OutputPath, []byte(content), 0o644)
 	}
 
 	// Print to stdout