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/skills/loader.py

@@ -1,9 +1,12 @@
+import logging
 import os
 from pathlib import Path
 
 from .parser import parse_skill_file
 from .types import Skill
 
+logger = logging.getLogger(__name__)
+
 
 def get_skills_root_path() -> Path:
     """
@@ -86,7 +89,7 @@ def load_skills(skills_path: Path | None = None, use_config: bool = True, enable
             skill.enabled = extensions_config.is_skill_enabled(skill.name, skill.category)
     except Exception as e:
         # If config loading fails, default to all enabled
-        print(f"Warning: Failed to load extensions config: {e}")
+        logger.warning("Failed to load extensions config: %s", e)
 
     # Filter by enabled status if requested
     if enabled_only: