Enhance API documentation and restructure routes for improved clarity

- Updated README.md to include comprehensive Swagger documentation details, highlighting new features and endpoint categories.
- Introduced a new router structure to streamline route registration for admin and public endpoints, enhancing maintainability.
- Updated health check endpoint documentation to reflect comprehensive server status information.
- Enhanced customer and company management routes with improved descriptions and examples in Swagger.
- Refactored customer and user handlers to remove obsolete route registrations, aligning with the new router structure.
- Improved response handling in customer and user services to utilize string IDs consistently.
- Updated validation rules and forms for customer management to support multiple company assignments.
- Enhanced logging practices across services to ensure better traceability and error handling.

docs/README.md

@@ -90,7 +90,7 @@ internal/{domain}/
 ### Structured Logging
 ```go
 log.Info("Customer authenticated successfully", map[string]interface{}{
-    "customer_id": customer.ID.String(),
+    "customer_id": customer.ID.Hex(),
     "email":       customer.Email,
     "ip":          clientIP,
 })