feat: add configurable log level and token usage tracking (#1301)

* feat: add configurable log level and token usage tracking

- Add `log_level` config to control deerflow module log level, synced
  to LangGraph Server via serve.sh `--server-log-level`
- Add `token_usage.enabled` config with TokenUsageMiddleware that logs
  input/output/total tokens per LLM call from usage_metadata
- Add .omc/ to .gitignore

* fix: use info level for token usage logs since feature has its own toggle

* fix: sort imports to pass lint check

---------

Co-authored-by: greatmengqi <chenmengqi.0376@bytedance.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/packages/harness/deerflow/config/app_config.py

@@ -17,6 +17,7 @@ from deerflow.config.skills_config import SkillsConfig
 from deerflow.config.subagents_config import load_subagents_config_from_dict
 from deerflow.config.summarization_config import load_summarization_config_from_dict
 from deerflow.config.title_config import load_title_config_from_dict
+from deerflow.config.token_usage_config import TokenUsageConfig
 from deerflow.config.tool_config import ToolConfig, ToolGroupConfig
 from deerflow.config.tool_search_config import ToolSearchConfig, load_tool_search_config_from_dict
 
@@ -28,6 +29,8 @@ logger = logging.getLogger(__name__)
 class AppConfig(BaseModel):
     """Config for the DeerFlow application"""
 
+    log_level: str = Field(default="info", description="Logging level for deerflow modules (debug/info/warning/error)")
+    token_usage: TokenUsageConfig = Field(default_factory=TokenUsageConfig, description="Token usage tracking configuration")
     models: list[ModelConfig] = Field(default_factory=list, description="Available models")
     sandbox: SandboxConfig = Field(description="Sandbox configuration")
     tools: list[ToolConfig] = Field(default_factory=list, description="Available tools")
@@ -163,8 +166,7 @@ class AppConfig(BaseModel):
 
         if user_version < example_version:
             logger.warning(
-                "Your config.yaml (version %d) is outdated — the latest version is %d. "
-                "Run `make config-upgrade` to merge new fields into your config.",
+                "Your config.yaml (version %d) is outdated — the latest version is %d. Run `make config-upgrade` to merge new fields into your config.",
                 user_version,
                 example_version,
             )