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/analytics/docs/index.md

@@ -0,0 +1,42 @@
+# Analytics & Reporting
+
+Dashboard analytics, custom reports, and data exports.
+
+## Overview
+
+| Aspect | Detail |
+|--------|--------|
+| Code | `analytics` |
+| Classification | Optional |
+| Dependencies | `catalog`, `inventory`, `marketplace`, `orders` |
+| Status | Active |
+
+## Features
+
+- `basic_reports` — Standard built-in reports
+- `analytics_dashboard` — Analytics dashboard widgets
+- `custom_reports` — Custom report builder
+- `export_reports` — Report data export
+- `usage_metrics` — Platform usage metrics
+
+## Permissions
+
+| Permission | Description |
+|------------|-------------|
+| `analytics.view` | View analytics and reports |
+| `analytics.export` | Export report data |
+| `analytics.manage_dashboards` | Create/edit custom dashboards |
+
+## Data Model
+
+Analytics primarily queries data from other modules (orders, inventory, catalog).
+
+## API Endpoints
+
+| Method | Path | Description |
+|--------|------|-------------|
+| `GET` | `/api/v1/store/analytics/*` | Store analytics data |
+
+## Configuration
+
+No module-specific configuration.