Reorganize repo: one folder per application under apps/.

Move docker/ and configs/ into apps/<name>/ with config/ subfolders.
Proxmox split into hosts/pve and hosts/dell-proxmox. Nginx under
infrastructure/. Update sync script, RESTORE.md, and per-app READMEs.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/portainer/docker-compose.yml

@@ -0,0 +1,13 @@
+# Portainer CE — Docker UI (poorten 8000, 9000).
+
+services:
+  portainer:
+    image: portainer/portainer-ce:latest
+    container_name: portainer
+    restart: always
+    ports:
+      - "${PORTAINER_EDGE:-8000}:8000"
+      - "${PORTAINER_HTTP:-9000}:9000"
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+      - ${PORTAINER_DATA_DIR:-/volume1/docker/portainer}:/data