chore(gitignore): fully ignore internal/web/dist, build stub included
The !internal/web/dist/.gitkeep exception kept the dist build stub
permanently visible as untracked noise and let it slip into commits four
separate times (each reverted with a 'drop the accidentally committed
dist build stub' commit). Nothing under dist/ is ever meant to be
tracked — make dist-stub and CI recreate the stub on disk — so drop the
whole exception block and let the plain dist/ rule cover it.