docs: retake README screenshots with seeded homelab data

All five shots recaptured against a live instance seeded with realistic
data: 20 services with dashboard-icons, 8 monitors, 4 real domains via
live WHOIS, 3 systems with the new chart grid, and a public status page.

Also references ghcr.io/dvorinka/dash:latest in docker-compose.yml so
`docker compose pull` works without a local build.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

docker-compose.yml

@@ -1,5 +1,8 @@
 services:
   dash:
+    # Prebuilt release image — `docker compose pull && docker compose up -d`.
+    # To build from source instead: `docker compose up -d --build`.
+    image: ghcr.io/dvorinka/dash:latest
     build:
       context: .
       dockerfile: infra/Dockerfile