docs: migrate module documentation to single source of truth

Move 39 documentation files from top-level docs/ into each module's
docs/ folder, accessible via symlinks from docs/modules/. Create
data-model.md files for 10 modules with full schema documentation.
Replace originals with redirect stubs. Remove empty guide stubs.

Modules migrated: tenancy, billing, loyalty, marketplace, orders,
messaging, cms, catalog, inventory, hosting, prospecting.

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

app/modules/hosting/docs/index.md

@@ -0,0 +1,49 @@
+# Hosting
+
+Web hosting, domains, email, and website building for Luxembourg businesses.
+
+## Overview
+
+| Aspect | Detail |
+|--------|--------|
+| Code | `hosting` |
+| Classification | Optional |
+| Dependencies | `prospecting` |
+| Status | Active |
+
+## Features
+
+- `hosting` — Web hosting management
+- `domains` — Domain registration and management
+- `email` — Email hosting
+- `ssl` — SSL certificate management
+- `poc_sites` — Proof-of-concept site builder
+
+## Permissions
+
+| Permission | Description |
+|------------|-------------|
+| `hosting.view` | View hosting data |
+| `hosting.manage` | Manage hosting services |
+
+## Data Model
+
+- **HostedSite** — Hosted website records
+- **ClientService** — Client service subscriptions
+
+## API Endpoints
+
+| Method | Path | Description |
+|--------|------|-------------|
+| `*` | `/api/v1/admin/hosting/*` | Admin hosting management |
+| `*` | `/api/v1/admin/hosting/services/*` | Service management |
+| `*` | `/api/v1/admin/hosting/sites/*` | Site management |
+| `GET` | `/api/v1/admin/hosting/stats/*` | Hosting statistics |
+
+## Configuration
+
+No module-specific configuration.
+
+## Additional Documentation
+
+- [User Journeys](user-journeys.md) — Hosting lifecycle user journeys