Claude Code: fix missing error_handlers.py in Docker build

- Added COPY error_handlers.py to Dockerfile to fix ModuleNotFoundError
- This file was being imported by app.py but wasn't copied to container

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -12,6 +12,7 @@ COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
 COPY app.py .
+COPY error_handlers.py .
 COPY openclaw.json .
 COPY openclaw/.openclaw /app/openclaw
 COPY static/ /app/static/