fix(system): add /api/v1/system/info endpoint for CLI diagnostics (M8, M11)

[BerryUIKI]

Summary

• Expose \GET /api/v1/system/info\ returning \HardwareReadiness\ model in FastAPI backend.
• Enables \�erry system\ and \�erry system --json\ CLI diagnostics commands to query hardware status, discrete GPU detection, backend acceleration flags, and storage readiness without 404 errors.
• Added comprehensive unit test in \�ackend/tests/test_m11_hardware.py\ verifying status 200 and schema completeness.