chore: take the version from VERSION.txt only (0.0.3)

VERSION.txt is embedded into the server and the agent, so a plain
go build reports the real version and build.sh no longer injects it.

internal/agent/client.go

@@ -18,12 +18,12 @@ import (
 	"runtime"
 	"time"
 
+	lpra "github.com/x-grk/longpolling-remote-access"
 	"github.com/x-grk/longpolling-remote-access/internal/proto"
 )
 
-// Version is the agent build version, injected at compile time via -ldflags
-// (-X .../internal/agent.Version=...).
-var Version = "dev"
+// Version is the agent build version (see VERSION.txt).
+var Version = lpra.Version
 
 // Config is the agent's runtime configuration (from env / config.env).
 type Config struct {