fix: replace print() with logging across harness package (#1282)

Replace all bare print() calls with proper logging using Python's
standard logging module across the deerflow harness package.

Changes across 8 files (16 print statements replaced):

- agents/middlewares/clarification_middleware.py: use logger.info/debug
- agents/middlewares/memory_middleware.py: use logger.debug
- agents/middlewares/thread_data_middleware.py: use logger.debug
- agents/middlewares/view_image_middleware.py: use logger.debug
- agents/memory/queue.py: use logger.info/debug/warning/error
- agents/lead_agent/prompt.py: use logger.error
- skills/loader.py: use logger.warning
- skills/parser.py: use logger.error

Each file follows the established codebase convention:
  import logging
  logger = logging.getLogger(__name__)

Log levels chosen based on message semantics:
- debug: routine operational details (directory creation, timer resets)
- info: significant state changes (memory queued, updates processed)
- warning: recoverable issues (config load failures, skipped updates)
- error: unexpected failures (parsing errors, memory update errors)

Note: client.py is intentionally excluded as it uses print() for
CLI output, which is the correct behavior for a command-line client.

Co-authored-by: moose-lab <moose-lab@users.noreply.github.com>

backend/packages/harness/deerflow/agents/middlewares/view_image_middleware.py

@@ -1,5 +1,6 @@
 """Middleware for injecting image details into conversation before LLM call."""
 
+import logging
 from typing import NotRequired, override
 
 from langchain.agents import AgentState
@@ -9,6 +10,8 @@ from langgraph.runtime import Runtime
 
 from deerflow.agents.thread_state import ViewedImageData
 
+logger = logging.getLogger(__name__)
+
 
 class ViewImageMiddlewareState(AgentState):
     """Compatible with the `ThreadState` schema."""
@@ -182,7 +185,7 @@ class ViewImageMiddleware(AgentMiddleware[ViewImageMiddlewareState]):
         # Create a new human message with mixed content (text + images)
         human_msg = HumanMessage(content=image_content)
 
-        print("[ViewImageMiddleware] Injecting image details message with images before LLM call")
+        logger.debug("Injecting image details message with images before LLM call")
 
         # Return state update with the new message
         return {"messages": [human_msg]}