fix(logging): replace structlog with stdlib logging to prevent broken pipe crashes

structlog fails with BrokenPipeError when stdout is redirected (e.g., background
processes, Docker logs). Replace all structlog.get_logger() calls with
logging.getLogger() and convert keyword-style log calls to %-format strings.

Also removes stale Docs/tasks.md (2028 lines) and updates Robot Framework
tests to match current API behavior.

src/server/api/websocket.py

@@ -342,7 +342,7 @@ async def websocket_endpoint(
         # Cleanup connection and rate limit record
         _cleanup_ws_rate_limits(connection_id)
         await ws_service.disconnect(connection_id)
-        logger.info("WebSocket connection closed", connection_id=connection_id)
+        logger.info("WebSocket connection closed connection_id=%s", connection_id)
 
 
 @router.get("/status")