Switch to cases/{new,in-progress,completed}/ directory structure

Replace single CASES_DIR with find_case_dir() that searches across
all status directories. New cases created in cases/new/{number}/.

Config: CASES_BASE, CASES_NEW, CASES_IN_PROGRESS, CASES_COMPLETED
Docker: added -v /home/chaim/legal-ai/cases:/cases volume mount

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/tools/workflow.py

@@ -44,7 +44,7 @@ async def workflow_status(case_number: str) -> str:
     from pathlib import Path
     from legal_mcp import config
 
-    case_dir = config.CASES_DIR / case_number
+    case_dir = config.find_case_dir(case_number)
     draft_path = case_dir / "drafts" / "decision.md"
     has_draft = draft_path.exists()
     draft_size = draft_path.stat().st_size if has_draft else 0