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

cmd/relspec/root.go

@@ -2,52 +2,22 @@ package main
 
 import (
 	"fmt"
-	"runtime/debug"
-	"time"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"github.com/spf13/cobra"
 )
 
+// version/buildDate mirror pkg/buildinfo so existing call sites keep working.
+// The actual values are set there via ldflags (see Makefile).
 var (
-	// Version information, set via ldflags during build
-	version          = "dev"
-	buildDate        = "unknown"
+	version          = buildinfo.Version
+	buildDate        = buildinfo.BuildDate
 	prisma7          bool
 	noVersion        bool
 	silent           bool
 	strictDirectives bool
 )
 
-func init() {
-	// If version wasn't set via ldflags, try to get it from build info
-	if version == "dev" {
-		if info, ok := debug.ReadBuildInfo(); ok {
-			// Try to get version from VCS
-			var vcsRevision, vcsTime string
-			for _, setting := range info.Settings {
-				switch setting.Key {
-				case "vcs.revision":
-					if len(setting.Value) >= 7 {
-						vcsRevision = setting.Value[:7]
-					}
-				case "vcs.time":
-					vcsTime = setting.Value
-				}
-			}
-
-			if vcsRevision != "" {
-				version = vcsRevision
-			}
-
-			if vcsTime != "" {
-				if t, err := time.Parse(time.RFC3339, vcsTime); err == nil {
-					buildDate = t.UTC().Format("2006-01-02 15:04:05 UTC")
-				}
-			}
-		}
-	}
-}
-
 var rootCmd = &cobra.Command{
 	Use:   "relspec",
 	Short: "RelSpec - Database schema conversion and analysis tool",