fix(modbus): zadne vecne pending v journalu + flock timeout + EV poll backoff
Zivy incident home-01 (TeltoCharge .16): zapis 15/19-20 koncil failed
s prazdnym error_msg, nebo zustal trvale pending a zablokoval exportni ticky.
- _gateway_exclusive: neblokujici flock s deadline (EMS_MODBUS_FLOCK_TIMEOUT_S,
default 20 s) -> GatewayLockTimeout misto starvation bez limitu
- execute_modbus_commands: invariant written/failed + neprazdny error_msg
(str(e) or repr(e)); safety net pres BaseException (CancelledError, chyba DB);
journal update mimo retry cyklus zarizeni; force_disconnect bez zamku brany
- telemetry poll_ev_chargers: po 3 selhanich backoff 5 min per (host,port,unit)
- mrtvy unit_id drzi branu 4x8=32 s z kazde minuty
- testy backend/tests/test_modbus_execute_failsafe.py; docs
modbus-command-journal.md (sekce Robustnost zapisu + konfigurace)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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