chore: point env_file at /mnt/storage/apps for caddy, pia-qbittorrent, cloudflare-ddns

.env files moved to the backed-up, non-source-controlled data dir
alongside each app's other state. immich and authentik keep a
symlink instead, since their compose.yml relies on ${VAR}
interpolation which Compose only resolves from a .env next to the
compose file (or via --env-file), not from the env_file: directive.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DPXhxhLUopnuDm3dWeHd5C

cloudflare-ddns/compose.yml

@@ -7,7 +7,7 @@ services:
     read_only: true
     cap_drop: [all]
     env_file:
-      - .env
+      - /mnt/storage/apps/cloudflare-ddns/.env
     environment:
       - DOMAINS=wampler.us
       - PROXIED=true