Honor quiet flag for early startup log messages

[citizen204]

Summary

With -q/--quiet/--silent, bandit still printed INFO messages emitted during option merging (e.g. [main] INFO Using ini file for skipped tests, [main] INFO Found project level .bandit file). The logger was initialized at INFO level at the top of main() and only lowered to WARN after argument/ini merging, so anything logged in between (notably _log_option_source() and _get_options_from_ini()) ignored the quiet flag.

This applies the same early sys.argv detection already used for -d/--debug to the quiet flags, so the logger starts at WARN when quiet is requested. Debug still takes precedence over quiet at startup, and the existing re-initialization logic later in main() is unchanged.

Verified: bandit --ini .bandit --silent target.py now emits no INFO lines, while output without --silent is unchanged.

Fixes #1250

Changes

• bandit/cli/main.py: detect quiet flags in sys.argv during early logger initialization