feat(writers): stamp RelSpec version in generated headers; preserve DBML column order

- Add pkg/buildinfo with Version/BuildDate (set via ldflags, VCS fallback);
  cmd/relspec now sources version info from it
- Emit "RelSpec <version> (built: <date>)" in generated file headers for
  bun, gorm, drizzle, pgsql (incl. migration), mssql, sqlite writers
- pgsql writer: getSortedColumns now sorts by Sequence then Name so the
  streaming WriteSchema/WriteDatabase path preserves source column order
- dbml reader: mergeTable re-bases merged-in column Sequence values past the
  existing max, fixing colliding sequences (and alphabetical fallback) when a
  table is split across multiple DBML files
- Tests for bun/gorm header + column order, and dbml multi-file merge ordering

pkg/writers/mssql/writer.go

@@ -11,6 +11,7 @@ import (
 
 	_ "github.com/microsoft/go-mssqldb" // MSSQL driver
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/mssql"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
@@ -68,7 +69,7 @@ func (w *Writer) WriteDatabase(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- MSSQL Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
-	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n\n")
+	fmt.Fprintf(w.writer, "-- Generated by %s\n\n", buildinfo.GeneratedComment())
 
 	// Process each schema in the database
 	for _, schema := range db.Schemas {
@@ -477,7 +478,7 @@ func (w *Writer) executeDatabaseSQL(db *models.Database, connString string) erro
 	statements := []string{}
 	statements = append(statements, "-- MSSQL Database Schema")
 	statements = append(statements, fmt.Sprintf("-- Database: %s", db.Name))
-	statements = append(statements, "-- Generated by RelSpec")
+	statements = append(statements, "-- Generated by "+buildinfo.GeneratedComment())
 
 	for _, schema := range db.Schemas {
 		if err := w.generateSchemaStatements(schema, &statements); err != nil {