Refactor demo session architecture: consolidate metadata into fixture files

This commit refactors the demo session architecture to consolidate all demo
configuration data into the fixture files, removing redundant metadata files.

## Changes Made:

### 1. Data Consolidation
- **Removed**: `shared/demo/metadata/demo_users.json`
- **Removed**: `shared/demo/metadata/tenant_configs.json`
- **Updated**: Merged all user data into `02-auth.json` files
- **Updated**: Merged all tenant config data into `01-tenant.json` files

### 2. Enterprise Parent Tenant Updates
- Updated owner name to "Director" (matching auth fixtures)
- Added description field matching tenant_configs.json
- Added `base_tenant_id` to all child tenant entries
- Now includes all 5 child locations (Madrid, Barcelona, Valencia, Seville, Bilbao)

### 3. Professional Tenant Updates
- Added description field from tenant_configs.json
- Ensured consistency with auth fixtures

### 4. Code Updates
- **services/tenant/app/api/internal_demo.py**:
  - Fixed child tenant staff members to use enterprise parent users
  - Changed from professional staff IDs to enterprise staff IDs (Laura López, José Martínez, Francisco Moreno)

- **services/demo_session/app/core/config.py**:
  - Updated DEMO_ACCOUNTS configuration with all 5 child outlets
  - Updated enterprise tenant name and email to match fixtures
  - Added descriptions for all child locations

- **gateway/app/middleware/demo_middleware.py**:
  - Updated comments to reference fixture files as source of truth
  - Clarified that owner IDs come from 01-tenant.json files

- **frontend/src/stores/useTenantInitializer.ts**:
  - Updated tenant names and descriptions to match fixture files
  - Added comments linking to source fixture files

## Benefits:

1. **Single Source of Truth**: All demo data now lives in fixture files
2. **Consistency**: No more sync issues between metadata and fixtures
3. **Maintainability**: Easier to update demo data (one place per tenant type)
4. **Clarity**: Clear separation between template data (fixtures) and runtime config

## Enterprise Demo Fix:

The enterprise owner is now correctly added as a member of all child tenants, fixing
the issue where the tenant switcher didn't show parent/child tenants and the
establishments page didn't load tenants for the demo enterprise user.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

shared/demo/fixtures/professional/01-tenant.json

@@ -6,6 +6,7 @@
     "email": "demo.professional@panaderiaartesana.com",
     "subscription_tier": "professional",
     "tenant_type": "standalone",
+    "description": "Professional tier demo tenant for bakery operations",
     "is_active": true,
     "created_at": "2025-01-15T06:00:00Z",
     "updated_at": "2025-01-15T06:00:00Z"