Add version line after banner with release date

Added mfer/constants.go with Version and ReleaseDate constants for
deterministic builds. Banner now shows "mfer by @sneak: v0.1.0 released 2025-12-17"

internal/cli/mfer.go

@@ -9,6 +9,7 @@ import (
 	"github.com/spf13/afero"
 	"github.com/urfave/cli/v2"
 	"sneak.berlin/go/mfer/internal/log"
+	"sneak.berlin/go/mfer/mfer"
 )
 
 // CLIApp is the main CLI application container. It holds configuration,
@@ -43,6 +44,7 @@ const banner = `
 func (mfa *CLIApp) printBanner() {
 	if log.GetLevel() <= log.InfoLevel {
 		_, _ = fmt.Fprintln(mfa.Stdout, banner)
+		_, _ = fmt.Fprintf(mfa.Stdout, "        mfer by @sneak: v%s released %s\n", mfer.Version, mfer.ReleaseDate)
 	}
 }
 

mfer/constants.go

@@ -0,0 +1,6 @@
+package mfer
+
+const (
+	Version     = "0.1.0"
+	ReleaseDate = "2025-12-17"
+)