Enable direct TUI apply

[NiceDayZc]

What changed

• removes the TUI hardware-write switch and typed APPLY interlock
• makes APPLY TO SPEAKER start the model-validated write immediately
• retains PID routing, band count, gain range, protocol validation, and audit logging
• updates the README, security notes, engineering audit, tests, and TUI screenshot

Why

The two-step interlock looked like an inactive placeholder and made the primary EQ workflow unnecessarily difficult. Direct apply makes the button behavior explicit while keeping packet-shape validation in the protocol layer.

Validation

• 44 tests passed
• full-package branch coverage: 68.93% (65% gate)
• Ruff, formatting, and mypy passed
• Bandit passed
• pip-audit found no known vulnerabilities
• wheel and sdist built successfully
• Twine checks passed