feat: pin ~28 images to specific versions, enable DIUN monitoring, add app-stacks pipeline
Pin third-party images from :latest to current stable versions:
- Platform: cloudflared, technitium, snmp-exporter, pve-exporter,
headscale, shadowsocks, xray
- Apps: paperless-ngx, linkwarden, wealthfolio, speedtest, synapse,
n8n, prowlarr, qbittorrent, lidarr, rybbit, ollama, immichframe,
cyberchef, networking-toolbox, echo, coturn, shlink, affine
Enable DIUN annotations on all pinned deployments with per-image
tag patterns. Add Woodpecker app-stacks pipeline for selective
terragrunt apply on changed app stacks.