✨ Parameterize file split function in data-process task

[Jasonxia007]

✨ Parameterize file split function in data-process task

DP_PART_PROCESSOR_COUNT：Celery 并行 process-part-worker 数量
DP_FILE_SPLIT_SIZE_MB：执行文件拆分的文档阈值

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🧪 Add telemetry data for knowledge base

[codecov]

Codecov Report

❌ Patch coverage is 80.38674% with 71 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
backend/utils/knowledge_telemetry.py	74.00%	37 Missing and 15 partials ⚠️
backend/data_process/tasks.py	83.58%	8 Missing and 3 partials ⚠️
backend/data_process/ray_actors.py	63.63%	4 Missing ⚠️
backend/data_process/worker.py	72.72%	3 Missing ⚠️
backend/data_process_service.py	0.00%	1 Missing ⚠️

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