docs: update documentation for /platforms/ URL routing strategy

- Add multi-platform URL routing section to url-routing/overview.md
- Update multi-platform-cms.md with new request flow diagrams
- Add PlatformContextMiddleware documentation to middleware.md
- Update middleware execution order diagram
- Add Phase 7 (Platform URL Routing Strategy) to implementation plan
- Update platform URL summary tables across all docs

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

docs/proposals/multi-platform-cms-architecture-implementation-plan.md

@@ -1,11 +1,12 @@
 # Multi-Platform CMS Architecture - Implementation Plan
 
-> **Status:** All Phases Complete (1-6)
+> **Status:** All Phases Complete (1-7)
 > **Last Updated:** 2026-01-19
 > **Commits:**
 > - `408019d` (Phase 1: Database & Models)
 > - `9680026` (Phases 2-5: Migration, Admin, Docs, Vendor Dashboard)
 > - `32bcbc8` (Phase 6: Loyalty Platform Setup)
+> - `a2407ae` (Phase 7: Platform URL Routing Strategy)
 
 ---
 
@@ -227,18 +228,79 @@ Inserts Loyalty platform with:
 
 ---
 
-## Documentation Requirements ✅ PARTIAL
+## Phase 7: Platform URL Routing Strategy ✅ COMPLETE
+
+### 7.1 URL Structure Changes
+
+**Previous approach (DEPRECATED):**
+- Development: `/oms/`, `/loyalty/` (first path segment = platform)
+- Ambiguity: `/faq` could be platform or page
+
+**New approach:**
+- Development: `/platforms/oms/`, `/platforms/loyalty/` (explicit prefix)
+- Main marketing site: `/` (no prefix) → `main` platform
+- Clear separation: `/faq` = main site, `/platforms/oms/faq` = OMS
+
+### 7.2 Implementation Details
+
+| Task | File | Status |
+|------|------|--------|
+| Update middleware URL detection | `middleware/platform_context.py` | ✅ |
+| Change DEFAULT_PLATFORM_CODE | `middleware/platform_context.py` | ✅ |
+| Remove hardcoded /oms, /loyalty routes | `main.py` | ✅ |
+| Update platform_pages.py homepage | `app/routes/platform_pages.py` | ✅ |
+| Add 'main' platform migration | `alembic/versions/z6g7h8i9j0k1_...py` | ✅ |
+
+### 7.3 URL Routing Summary
+
+| Platform | Code | Dev URL | Prod URL |
+|----------|------|---------|----------|
+| Main Marketing | `main` | `localhost:9999/` | `wizamart.lu/` |
+| OMS | `oms` | `localhost:9999/platforms/oms/` | `oms.lu/` |
+| Loyalty | `loyalty` | `localhost:9999/platforms/loyalty/` | `loyalty.lu/` |
+
+### 7.4 Middleware Detection Logic
+
+```
+Request arrives
+      │
+      ▼
+┌─────────────────────────────────────┐
+│ Production domain? (oms.lu, etc.)   │
+└─────────────────────────────────────┘
+      │ YES → Route to that platform
+      │
+      ▼ NO (localhost)
+┌─────────────────────────────────────┐
+│ Path starts with /platforms/{code}? │
+└─────────────────────────────────────┘
+      │ YES → Strip prefix, route to platform
+      │       /platforms/oms/pricing → /pricing
+      │
+      ▼ NO
+┌─────────────────────────────────────┐
+│ Use 'main' platform (DEFAULT)       │
+│ /faq → Main site FAQ page           │
+└─────────────────────────────────────┘
+```
+
+---
+
+## Documentation Requirements ✅ COMPLETE
 
 ### Architecture Documentation ✅ COMPLETE
 
-Created `docs/architecture/multi-platform-cms.md`:
+Updated documentation for Phase 7:
+- [x] `docs/architecture/url-routing/overview.md` - Multi-platform URL routing section
+- [x] `docs/architecture/multi-platform-cms.md` - Request flow with path rewriting
+- [x] `docs/architecture/middleware.md` - PlatformContextMiddleware documentation
 - [x] Three-tier content hierarchy explanation
 - [x] Platform vs Vendor Default vs Vendor Override
 - [x] Database schema diagrams
 - [x] Request flow diagrams
 - [x] API endpoints reference
 - [x] Key files reference
-- [x] Adding new platform guide
+- [x] Adding new platform guide with URL summary
 
 ### API Documentation
 
@@ -253,6 +315,7 @@ Included in `docs/architecture/multi-platform-cms.md`:
 - [x] Step-by-step platform creation
 - [x] Required database records
 - [x] Key files reference
+- [x] Platform URL summary table
 
 ---
 
@@ -297,17 +360,34 @@ Customer visits: oms.lu/vendors/wizamart/about
 
 ---
 
-## Next Session Checklist
+## Verification Checklist
 
-Start here when resuming work:
+All phases are complete. Use these commands to verify:
 
-1. [ ] Run `alembic upgrade head` (backup DB first!)
-2. [ ] Verify migration: `SELECT * FROM platforms;`
-3. [ ] Register PlatformContextMiddleware in `main.py`
-4. [ ] Update VendorContextMiddleware to use `platform_clean_path`
-5. [ ] Fix platform homepage to use CMS
-6. [ ] Test: `localhost:9999/oms/` shows CMS homepage
-7. [ ] Test: Three-tier resolution works
+```bash
+# 1. Check platforms in database
+psql -d wizamart -c "SELECT code, name, domain FROM platforms;"
+# Expected: main, oms, loyalty
+
+# 2. Test main marketing site
+curl -s localhost:9999/ | grep -o "<title>.*</title>"
+# Expected: Main marketing site title
+
+# 3. Test OMS platform
+curl -s localhost:9999/platforms/oms/ | grep -o "<title>.*</title>"
+# Expected: OMS platform title
+
+# 4. Test Loyalty platform
+curl -s localhost:9999/platforms/loyalty/ | grep -o "<title>.*</title>"
+# Expected: Loyalty platform title
+
+# 5. Verify middleware detection
+python -c "
+from middleware.platform_context import PlatformContextMiddleware, DEFAULT_PLATFORM_CODE
+print(f'DEFAULT_PLATFORM_CODE: {DEFAULT_PLATFORM_CODE}')
+# Expected: main
+"
+```
 
 ---