fix: apply S3 environment variables during initial setup

[Nerahikada]

Description

S3 environment variables (GOKAPI_AWS_*) were ignored during initial setup due to an early return in loadFromConfig() and a template guard that skipped cloud storage auto-selection.
This fix ensures they are loaded and applied on first run.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor / Chore

Technical Details

• Database changes: No
• Storage backend affected: No
• Usage of AI: Yes - Bug investigation, fix implementation, and commit messages were assisted

How Has This Been Tested?

• Manual Testing: Set all GOKAPI_AWS_* env vars via Docker Compose, verified initial setup auto-selects Cloud Storage and shows "credentials provided with environment variables"
• Unit Tests: go test -tags test ./internal/configuration/setup/
• Environment: Docker (Podman Compose), Linux

Checklist

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.

[Forceu]

Thank you very much for the PR! This must have been broken in one of the previous updates.