Treat undefined config options as silent fallback in Config::getOption

[BinqAdams]

Summary

Stop logging "Option failed to parse" when a bridge config option is simply not defined. Real parse failures (value present but malformed) still warn.

Motivation

Config::getOption<T> (in bridge/src/util/config/config.h) previously logged Logger::warn("Option failed to parse: <name>") whenever the option wasn't defined in any config file — the empty looked-up value would fall through to parseOptionValue, which fails on empty input. Several options are read on hot paths (e.g. client.optimizedDynamicLock fires from the LockableBuffer ctor); a per-call warning floods the log at high frequency under heavy buffer creation.

An empty looked-up value semantically means the option is undefined, which is exactly what the fallback parameter is for — the explicit contract for absence.

What Changed

bridge/src/util/config/config.h: in Config::getOption<T>, short-circuit to the supplied fallback when getOptionValue(option) returns an empty string. Real parse failures (non-empty value that fails parseOptionValue) still emit the Logger::warn as before.

Net diff: bridge/src/util/config/config.h only, +5.

Testing

Verified that:

• Options not defined in any config now silently use their fallback (no log emission).
• Options defined with valid values continue to parse correctly.
• Options defined with malformed values still emit the parse-failure warning.

The behavioral change is limited to the absent-option case, which previously logged but otherwise returned the same fallback value.