fix: highlight the interface mode toggle

[Minorli]

Summary

• style the simple/professional mode switch with the existing primary green palette
• add hover, active, and keyboard-focus states without changing toggle behavior
• release as 0.1.65 with synchronized cache keys and image metadata

Verification

• ./scripts/check.sh (411 passed)
• tests/test_static_assets.py (69 passed)
• pip-audit (no known vulnerabilities)
• Playwright desktop 1440x900 and mobile 375x812 render checks; no horizontal overflow
• no real image-generation requests were made