refactor: remove all backward compatibility code across 70 files

Clean up 28 backward compatibility instances identified in the codebase.
The app is not live, so all shims are replaced with the target architecture:

- Remove legacy Inventory.location column (use bin_location exclusively)
- Remove dashboard _extract_metric_value helper (use flat metrics dict)
- Remove legacy stat field duplicates (total_stores, total_imports, etc.)
- Remove 13 re-export shims and class aliases across modules
- Remove module-enabling JSON fallback (use PlatformModule junction table)
- Remove menu_to_legacy_format() conversion (return dataclasses directly)
- Remove title/description from MarketplaceProductBase schema
- Clean billing convenience method docstrings
- Clean test fixtures and backward-compat comments
- Add PlatformModule seeding to init_production.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/architecture/url-routing/overview.md

@@ -63,14 +63,14 @@ Orion supports multiple platforms (OMS, Loyalty, Site Builder), each with its ow
 |-----|----------------|
 | `orion.lu/` | Main marketing site homepage |
 | `orion.lu/about` | Main marketing site about page |
-| `oms.lu/` | OMS platform homepage |
-| `oms.lu/pricing` | OMS platform pricing page |
-| `oms.lu/admin/` | Admin panel for OMS platform |
-| `oms.lu/store/{code}/` | Store dashboard on OMS |
+| `omsflow.lu/` | OMS platform homepage |
+| `omsflow.lu/pricing` | OMS platform pricing page |
+| `omsflow.lu/admin/` | Admin panel for OMS platform |
+| `omsflow.lu/store/{code}/` | Store dashboard on OMS |
 | `https://mybakery.lu/storefront/` | Store storefront (store's custom domain) |
-| `loyalty.lu/` | Loyalty platform homepage |
+| `rewardflow.lu/` | Loyalty platform homepage |
 
-**Note:** In production, stores configure their own custom domains for storefronts. The platform domain (e.g., `oms.lu`) is used for admin and store dashboards, while storefronts use store-owned domains.
+**Note:** In production, stores configure their own custom domains for storefronts. The platform domain (e.g., `omsflow.lu`) is used for admin and store dashboards, while storefronts use store-owned domains.
 
 ### Quick Reference by Platform
 
@@ -83,9 +83,9 @@ Dev:
   Storefront: http://localhost:8000/platforms/oms/stores/{store_code}/storefront/
 
 Prod:
-  Platform:   https://oms.lu/
-  Admin:      https://oms.lu/admin/
-  Store:     https://oms.lu/store/{store_code}/
+  Platform:   https://omsflow.lu/
+  Admin:      https://omsflow.lu/admin/
+  Store:     https://omsflow.lu/store/{store_code}/
   Storefront: https://mybakery.lu/storefront/  (store's custom domain)
 ```
 
@@ -98,9 +98,9 @@ Dev:
   Storefront: http://localhost:8000/platforms/loyalty/stores/{store_code}/storefront/
 
 Prod:
-  Platform:   https://loyalty.lu/
-  Admin:      https://loyalty.lu/admin/
-  Store:     https://loyalty.lu/store/{store_code}/
+  Platform:   https://rewardflow.lu/
+  Admin:      https://rewardflow.lu/admin/
+  Store:     https://rewardflow.lu/store/{store_code}/
   Storefront: https://myrewards.lu/storefront/  (store's custom domain)
 ```
 
@@ -112,7 +112,7 @@ Request arrives
       ▼
 ┌─────────────────────────────────────┐
 │ Check: Is this production domain?   │
-│ (oms.lu, loyalty.lu, etc.)          │
+│ (omsflow.lu, rewardflow.lu, etc.)          │
 └─────────────────────────────────────┘
       │
       ├── YES → Route to that platform
@@ -139,8 +139,8 @@ Request arrives
 | Platform | Code | Dev URL | Prod Domain |
 |----------|------|---------|-------------|
 | Main Marketing | `main` | `localhost:8000/` | `orion.lu` |
-| OMS | `oms` | `localhost:8000/platforms/oms/` | `oms.lu` |
-| Loyalty | `loyalty` | `localhost:8000/platforms/loyalty/` | `loyalty.lu` |
+| OMS | `oms` | `localhost:8000/platforms/oms/` | `omsflow.lu` |
+| Loyalty | `loyalty` | `localhost:8000/platforms/loyalty/` | `rewardflow.lu` |
 | Site Builder | `site-builder` | `localhost:8000/platforms/site-builder/` | `sitebuilder.lu` |
 
 **See:** [Multi-Platform CMS Architecture](../multi-platform-cms.md) for content management details.