fix(writers): drop version stamps from generated output

Generated files carried the RelSpec version and build date, so every
rebuild produced a diff even when the schema was unchanged.

- bun, gorm, drizzle: remove the GeneratedBy template field and line
- pgsql, mssql, sqlite: emit a constant "-- Generated by RelSpec"
- bun: replace the version header test with a version-free assertion

pkg/buildinfo is unchanged and still backs the CLI version.

pkg/writers/gorm/template_data.go

@@ -4,7 +4,6 @@ import (
 	"sort"
 	"strings"
 
-	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -12,7 +11,6 @@ import (
 // TemplateData represents the data passed to the template for code generation
 type TemplateData struct {
 	PackageName string
-	GeneratedBy string
 	Imports     []string
 	Models      []*ModelData
 	Config      *MethodConfig
@@ -81,7 +79,6 @@ func NewTemplateData(packageName string, config *MethodConfig) *TemplateData {
 
 	return &TemplateData{
 		PackageName: packageName,
-		GeneratedBy: buildinfo.GeneratedComment(),
 		Imports:     make([]string, 0),
 		Models:      make([]*ModelData, 0),
 		Config:      config,