Flatten cases directory structure and unify paths

- Remove cases/new|in-progress|completed subdivision (status managed in DB)
- Rename documents/original → documents/originals (consistent plural)
- Move exports from global data/exports/ into cases/{num}/exports/
- Add documents/research/ for case law and analysis files
- Update all agents, scripts, config, web API endpoints, and DB paths

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

mcp-server/src/legal_mcp/services/lessons.py

@@ -1,6 +1,6 @@
 """Lessons learned from comparing AI drafts to Dafna Tamir's final decisions.
 
-Source: /data/uploads/לקחים-לעדכון-שרת-כתיבת-החלטות.md
+Source: docs/legal-decision-lessons.md
 Based on analysis of: Hecht 1180-1181 (rejection) and Beit HaKerem 1126/25+1141/25 (partial acceptance).
 """