fix: Use AsyncSession in some non-blocking APIs

[cbornet]

Fix sync/async DB usage in APIs:

• flows
• files
• folders
• monitor

[codspeed-hq]

CodSpeed Performance Report

Merging #4484 will degrade performances by 16.28%

_{Comparing cbornet:async-db-apis (a730d2d) with main (19963de)}

Summary

⚡ 2 improvements
❌ 2 regressions
✅ 11 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	cbornet:async-db-apis	Change
⚡	test_invalid_run_with_input_type_chat	18.3 ms	14 ms	+30.92%
❌	test_successful_run_with_input_type_any	457.5 ms	546.5 ms	-16.28%
❌	test_successful_run_with_output_type_any	455.5 ms	532.3 ms	-14.42%
⚡	test_successful_run_with_output_type_debug	509.8 ms	455 ms	+12.04%