feat: async OCR workflow - split submit + poll tools to avoid timeout issues

- Add submit_pdf_for_ocr() - submits immediately, returns task_id
- Add get_ocr_result() - polls for completion, saves Markdown
- Keep batch_ocr_pdf() as deprecated fallback
- Update README with new async usage pattern
- Update pyproject.toml description

pyproject.toml

@@ -5,11 +5,12 @@ build-backend = "hatchling.build"
 [project]
 name = "procleaning-mcp"
 version = "0.1.0"
-description = "Python MCP Server for process monitoring and cleaning"
+description = "Python MCP Server for PDF OCR async processing and system process utilities"
 readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
     "mcp>=1.0.0",
+    "aiohttp>=3.9.0",
     "requests>=2.31.0",
 ]