Bridge: set_lnb_voltage(mode) wraps firmware lnbdc command, enable_lna() now delegates to it. MCP: new set_lnb_voltage tool + 3 tests. TUI: Signal screen button toggles between V-pol and H-pol instead of one-way LNA enable.
34 tools (connection, movement, signal, system, satellite, console), 5 resources, 3 prompts. Backed by DemoDevice for offline testing. 46 tests passing against the demo backend via run_server_async.
