fix: unauthorized get templates fetch

[Schwehn42]

Description

currently, the frontend will attempt to fetch templates even if the user isn't allowed to (e.g. https://docs.scrumlr.io/self-hosting/env-vars/#allow-anonymous-template-creation).
the backend would respond with a 403.

this PR checks if the user is supposed to see custom templates and only makes the call if yes.

Changelog

• rm duplicate template fetch in Boards
• make template fetch conditional

Checklist

• I have performed a self-review of my own code
• I have written and understand every part of this contribution myself - if AI tools were used, I have thoroughly reviewed and verified all changes
• I have commented my code, particularly in hard-to-understand areas

[github-actions]

The deployment to the dev cluster was successful. You can find the deployment here: https://6527.development.scrumlr.fra.ics.inovex.io
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Deployed Images

• ghcr.io/inovex/scrumlr.io/scrumlr-frontend:sha-a4e5ece

• ghcr.io/inovex/scrumlr.io/scrumlr-server:sha-a4e5ece

[Planlos5000]

LGTM