docs: add tenancy module migration plan and session notes

DOCUMENTATION:
- docs/architecture/tenancy-module-migration.md
  - Complete migration plan for tenancy module
  - Files to migrate: routes, services, models, schemas
  - Files to keep in root (framework level)
  - Files for other modules (messaging, cms, monitoring, core)
  - Target module structure
  - Recommended migration order

- docs/proposals/SESSION_NOTE_2026-01-31_tenancy-module-consolidation.md
  - Session summary and key decisions
  - Module ownership assignments
  - Next actions and priorities

Key principle: Tenancy owns identity and organizational hierarchy.
Everything else belongs to feature modules.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/proposals/SESSION_NOTE_2026-01-31_tenancy-module-consolidation.md

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+# Session Note: Tenancy Module Consolidation Plan
+
+**Date:** 2026-01-31
+**Topic:** Complete migration plan for tenancy module and remaining legacy code
+
+## Summary
+
+This session established a comprehensive plan for migrating all identity and organizational management code to the tenancy module, plus identified where other legacy code should go.
+
+## Key Decisions
+
+### 1. Tenancy Module Scope
+
+The tenancy module owns **identity and organizational hierarchy**:
+- Platforms (top-level SaaS instances)
+- Companies (business entities)
+- Vendors (merchant accounts)
+- Users (admin users, team members)
+- Authentication (login, tokens, sessions)
+- Teams (vendor team management)
+- Domains (custom domain configuration)
+
+### 2. Completed Migrations (This Session)
+
+- Migrated `app/api/v1/vendor/info.py` → `tenancy/routes/api/vendor.py`
+- Changed path from `/{vendor_code}` to `/info/{vendor_code}` (removes catch-all)
+- Set up tenancy module as `is_self_contained=True`
+- Updated frontend JS to use new endpoint path
+
+### 3. Files Identified for Tenancy Migration
+
+#### Routes to Migrate
+```
+Admin API:
+- admin_users.py    → tenancy/routes/api/admin_users.py
+- companies.py      → tenancy/routes/api/admin_companies.py
+- platforms.py      → tenancy/routes/api/admin_platforms.py
+- vendors.py        → tenancy/routes/api/admin_vendors.py
+- vendor_domains.py → tenancy/routes/api/admin_vendor_domains.py
+- users.py          → tenancy/routes/api/admin_users.py
+- auth.py           → tenancy/routes/api/admin_auth.py
+
+Vendor API:
+- auth.py           → tenancy/routes/api/vendor_auth.py
+- profile.py        → tenancy/routes/api/vendor_profile.py
+- team.py           → tenancy/routes/api/vendor_team.py
+```
+
+#### Services to Migrate
+```
+- vendor_service.py
+- company_service.py
+- platform_service.py
+- admin_service.py
+- admin_platform_service.py
+- vendor_domain_service.py
+- vendor_team_service.py
+- team_service.py
+- auth_service.py
+- platform_signup_service.py
+```
+
+#### Models to Migrate
+```
+- vendor.py
+- company.py
+- platform.py
+- admin.py
+- admin_platform.py
+- vendor_domain.py
+- vendor_platform.py
+- user.py
+```
+
+### 4. Other Module Assignments
+
+| Module | Files to Receive |
+|--------|-----------------|
+| **monitoring** | background_tasks, logs, monitoring, platform_health, audit |
+| **dev_tools** | code_quality, tests |
+| **messaging** | messages, notifications, email_templates, email_settings |
+| **cms** | media, images, vendor_themes |
+| **core** (new) | dashboard, settings |
+
+### 5. Framework-Level (Stay in ROOT)
+
+- Module system (`modules.py`, `module_config.py`)
+- Menu configuration (`menu_config.py`)
+- System settings (`settings.py`)
+- Base models (`base.py`, `platform_module.py`, `admin_menu_config.py`)
+
+## Architecture Validation Updates
+
+Added new rules to enforce module-first architecture:
+- **MOD-016**: Routes must be in modules, not `app/api/v1/`
+- **MOD-017**: Services must be in modules, not `app/services/`
+- **MOD-018**: Tasks must be in modules, not `app/tasks/`
+- **MOD-019**: Schemas must be in modules, not `models/schema/`
+
+## Documentation Created
+
+1. `docs/architecture/tenancy-module-migration.md` - Full migration plan
+2. `docs/development/migration/module-autodiscovery-migration.md` - Migration history
+3. Updated `docs/architecture/module-system.md` - Entity auto-discovery reference
+
+## Next Actions
+
+### Immediate (High Priority)
+1. Migrate vendor auth routes to tenancy
+2. Migrate admin auth routes to tenancy
+3. Migrate vendor profile and team routes
+
+### Short-term
+4. Migrate company/vendor/platform admin routes
+5. Move services to tenancy module
+6. Create re-exports for backwards compatibility
+
+### Medium-term
+7. Migrate models to tenancy (careful - many dependencies)
+8. Migrate schemas
+9. Move messaging routes to messaging module
+10. Move media routes to cms module
+
+### Long-term
+11. Create core module for dashboard/settings
+12. Remove all re-exports once migration complete
+13. Archive legacy directories
+
+## Commits This Session
+
+1. `401db56` - refactor: migrate remaining routes to modules and enforce auto-discovery
+2. `23d5949` - refactor: move vendor info endpoint to tenancy module
+
+## Key Principle
+
+> **Tenancy owns identity and organizational hierarchy.**
+> Everything else belongs to feature modules.
+
+## Related Files
+
+- `/docs/architecture/tenancy-module-migration.md`
+- `/docs/architecture/module-system.md`
+- `/docs/development/migration/module-autodiscovery-migration.md`
+- `/.architecture-rules/module.yaml`
+- `/scripts/validate_architecture.py`