chore: [#28] remove obsolete container configuration directory

- Remove application/share/container/default/config/crontab.conf
- Update documentation references to reflect template-based architecture
- Modernize configuration management by using infrastructure/config/templates/
- Clean up legacy container configuration patterns

The cron configuration is now managed through the template system in
infrastructure/config/templates/crontab/ as part of the deployment process.

Author: josecelano

application/README.md

@@ -24,11 +24,6 @@ application/
 │   │   ├── time-running.sh
 │   │   ├── tracker-db-backup.sh
 │   │   └── tracker-filtered-logs.sh
-│   ├── container/default/config/  # Container configurations
-│   │   ├── crontab.conf
-│   │   ├── nginx.conf
-│   │   ├── prometheus.yml
-│   │   └── tracker.prod.container.sqlite3.toml
 │   ├── dev/home/             # Development configurations
 │   └── grafana/dashboards/   # Grafana dashboard configurations
 │       ├── metrics.json

application/docs/backups.md

@@ -13,9 +13,8 @@ cd /home/torrust/github/torrust/torrust-tracker-demo/
 sudo crontab -e
 ```
 
-You should see the
-[crontab.conf](../share/container/default/config/crontab.conf) configuration
-file.
+You should see the MySQL backup cron job configured from the template system in
+`infrastructure/config/templates/crontab/mysql-backup.cron`.
 
 ## Check Backups
 

application/share/container/default/config/crontab.conf

@@ -46,7 +46,7 @@ grep torrust-demo.dev /etc/hosts
 
 The nginx proxy configuration is generated from templates during deployment:
 
-- **Template**: `application/share/container/proxy/nginx.conf.j2` (if exists)
+- **Template**: `infrastructure/config/templates/proxy/` (template-based configuration)
 - **Generated Config**: `/var/lib/torrust/proxy/nginx.conf` (on server)
 - **SSL Certificates**: `/var/lib/torrust/proxy/certs/` and `/var/lib/torrust/proxy/private/`
 
@@ -130,13 +130,15 @@ curl -k -I https://grafana.torrust-demo.dev
 
 1. **Create nginx configuration template:**
 
-Create `application/share/container/proxy/nginx.conf.tpl` with complete configuration including Grafana subdomain support.
+Create nginx configuration templates in `infrastructure/config/templates/proxy/`  
+with complete configuration including Grafana subdomain support.
 
-2. **Update deployment script:**
+1. **Update deployment script:**
 
-Modify `infrastructure/scripts/deploy-app.sh` to process the nginx template and generate configuration with both tracker and Grafana subdomains.
+Modify `infrastructure/scripts/deploy-app.sh` to process the nginx template and  
+generate configuration with both tracker and Grafana subdomains.
 
-3. **Add environment variables:**
+1. **Add environment variables:**
 
 ```bash
 # In your environment configuration