Add AsyncDbWorker: a persistent background thread with dedup queue that
executes DB2 writes asynchronously, keeping the mon 20ms cycle free of
blocking I/O.
Changes:
- async_db_worker.h/.cc: singleton worker, submit() with rule_id dedup,
drain_and_stop() for clean shutdown
- eqp_stat.h/.cc: new update_static(ruleid, shear_times, running_time)
overload that skips redundant DB reads for known values (reduces
5 SELECTs to 3 per persist cycle)
- exp_times.cc: extract persist_exp_times() as a standalone function,
update_history_times() snapshots values and submits to worker
(returns immediately), reset_dev_data() uses direct SHM update
- eqpalg_icei.cpp: alg_mgr_.reset() → drain_and_stop() in destructor
ensures all algorithm threads are stopped before draining the worker
Risk: re-run cmake .. to pick up the new async_db_worker.cc file.
Display data (alarm_value, current_value, limit_up/down, items, unit) now
goes to a local-memory DisplayCache and is serialized to JSON without any
shared memory lock. Cold data (stat_values, running_time, shear_times, etc.)
stays in shared memory for mon-cron IPC, protected by a real interprocess
mutex (boost::interprocess::interprocess_mutex) instead of the broken
process-local std::mutex. AlgBase::rule_stat_ is now RuleStatLocal with
standard types — zero changes to algorithm subclass code.
