The websearch_firecrawl_key config key was added in PR #7764 (Firecrawl
web search provider) but was missing from DEFAULT_CONFIG in default.py.
Because AstrBotConfig.check_config_integrity() removes keys that exist
in the user's cmd_config.json but are absent from DEFAULT_CONFIG, the
firecrawl API key is silently deleted on every container restart.
Fixes: unreported issue (config key removed on restart)