fix(config): add missing websearch_firecrawl_key to DEFAULT_CONFIG (#8012)

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)

astrbot/core/config/default.py

@@ -111,6 +111,7 @@ DEFAULT_CONFIG = {
         "websearch_bocha_key": [],
         "websearch_brave_key": [],
         "websearch_baidu_app_builder_key": "",
+        "websearch_firecrawl_key": [],
         "web_search_link": False,
         "display_reasoning_text": False,
         "identifier": False,