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/duckdns/docker-compose.yml

@@ -0,0 +1,16 @@
+# DuckDNS — dynamisch DNS voor mohome020.duckdns.org
+# Start: cp .env.example .env && docker compose up -d
+
+services:
+  duckdns:
+    image: linuxserver/duckdns:latest
+    container_name: duckdns
+    restart: unless-stopped
+    environment:
+      PUID: ${PUID:-1026}
+      PGID: ${PGID:-100}
+      TZ: ${TZ:-Europe/Brussels}
+      SUBDOMAINS: ${DUCKDNS_SUBDOMAINS:-mohome020}
+      TOKEN: ${DUCKDNS_TOKEN:-8787f708-da03-41ed-97de-306436021d91}
+      UPDATE_IP: ${DUCKDNS_UPDATE_IP:-true}
+      INTERVAL: ${DUCKDNS_INTERVAL:-300}