refactor : reorganize infra files into infra/dev and infra/prod

Consolidate Docker, Nginx, and deploy configs from 5 scattered directories
(docker/, deploy/docker/, deploy/nginx/, script/) into a single infra/ tree
with dev/ and prod/ subdirectories. Update all references in docker-compose,
Makefile, CI workflows, Dockerfiles, and documentation.

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

.gitea/workflows/build-docker.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Build Docker image
         run: |
           docker build \
-            -f deploy/docker/Dockerfile.prod \
+            -f infra/prod/Dockerfile \
             -t gitea.malio.fr/malio-dev/lesstime:${{ gitea.ref_name }} \
             -t gitea.malio.fr/malio-dev/lesstime:latest \
             .