feat(logging)!: add enhanced logging system
BREAKING CHANGE: stk_log() signature changed to require log level
- Add log levels (ERROR, WARN, INFO, DEBUG) with runtime filtering
- Add timestamps (yyyy-mm-dd HH:MM:SS.mmm format)
- Add stk_set_log_output(), stk_set_log_prefix(), stk_set_log_level()
- Platform-specific timestamp: GetLocalTime (Windows), gettimeofday (POSIX)
- Consolidate duplicate platform includes into POSIX common block
- Setting log output to NULL disables logging.
Default: INFO level, "stk" prefix, stdout output. All internal messages
use appropriate severity levels. Single byte flag controls enable/disable.
anth64
110b7ffca8