feat(planning): add comprehensive BCSDLab INTERNAL work plan

- 13 detailed tasks across 4 waves (45-70 hours estimated)
- Complete business logic specifications:
  - Fee lifecycle model (payment-logging, state machine)
  - Data migration specification (column mapping, dedup rules)
  - ID/FK strategy with concrete examples
- Verified through 3 Momus review iterations
- Production-ready with concrete acceptance criteria
- Includes n8n workflows, Google Workspace integration, optional FastAPI+SpiceDB

Project: BCSDLab club management automation system
Stack: n8n + Google Workspace (Sheets as DB) + optional FastAPI
Goal: Automate fee tracking, member lifecycle, administrative tasks

Author: ImTotem