refactor : rename Inventory_frontend to frontend everywhere

Update Dockerfile, nginx, .dockerignore, makefile, CI workflow,
CLAUDE.md, README, release script to use frontend/ instead of
Inventory_frontend/. Remove submodule references from CI and
release script.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-docker.yml

@@ -11,8 +11,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-        with:
-          submodules: true
 
       - name: Login to Gitea Registry
         run: |