fix: set MinPasswordLength in reconfiguration setup view

[Nerahikada]

Description

loadFromConfig() only set MinPasswordLength in the initial-setup path, so the reconfiguration UI rendered password fields with data-min=0, bypassing client-side minimum-length validation. (Found during investigation of #370.)

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 GOKAPI_MIN_LENGTH_PASSWORD=16, ran --reconfigure, and confirmed the password field enforces 16-char minimum
• 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