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/sqlite/writer.go

@@ -10,7 +10,6 @@ import (
 
 	_ "modernc.org/sqlite" // SQLite driver
 
-	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -73,7 +72,7 @@ func (w *Writer) writeContent(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- SQLite Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
-	fmt.Fprintf(w.writer, "-- Generated by %s\n", buildinfo.GeneratedComment())
+	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
 	fmt.Fprintf(w.writer, "-- Note: SQLite has no schema concept; non-default schema names are flattened into table name prefixes (e.g., auth.sessions -> auth_sessions)\n\n")
 
 	// Enable foreign keys