fix(supervisor-network): warn on unsupported L7 access presets

[deepujain]

Summary

• warn when an L7 endpoint uses an unsupported access preset without explicit rules
• keep startup non-blocking for unsupported REST-style presets while making the ignored policy visible
• add regression coverage for an unsupported access: allow preset

Closes #2008

Testing

• cargo fmt --check
• cargo test -p openshell-supervisor-network validate_unsupported_access_preset_warns
• cargo test -p openshell-supervisor-network
• cargo clippy -p openshell-supervisor-network --all-targets -- -D warnings
• mise run pre-commit

Notes

Opened as draft from a fork so it can be moved to ready-for-review after the contributor vouch step if required.

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[deepujain]

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[deepujain]

recheck