apps: fix default ports

[stavros-k]

Changed default ports to ensure unique default ports per app.
Added a basic script to check for duplicates and fail CI if found, which also gives the next 5 free ports

Closes #1512

[github-actions]

Stable

Diskoverdata

Affected areas: metadata, ui
Modified files:

• app.yaml
• questions.yaml

---

Home-Assistant

Affected areas: metadata, ui
Modified files:

• app.yaml
• questions.yaml

---

Prometheus

Affected areas: metadata, ui
Modified files:

• app.yaml
• questions.yaml

---

Notifying the following about changes to the trains:
@truenas/docs-team

[yocalebo]

listdir is painfully slow. scandir is the preferred method