Remove obsolete customer endpoint and update related documentation

- Deleted the `/admin/v1/customers/{id}/with-companies` endpoint from the API documentation and Swagger files to streamline the API structure.
- Updated the router to remove the corresponding route registration for the deprecated endpoint.
- Enhanced the company repository and service to support batch retrieval of companies by IDs, improving efficiency in data handling.
- Adjusted customer service methods to utilize the new batch retrieval functionality for loading companies associated with customers.
- Improved logging practices to provide better traceability for company retrieval operations.

cmd/web/docs/swagger.yaml

@@ -2546,47 +2546,6 @@ paths:
       summary: Verify customer
       tags:
       - Admin-Customers
-  /admin/v1/customers/{id}/with-companies:
-    get:
-      consumes:
-      - application/json
-      description: Retrieve detailed customer information by customer ID including
-        assigned companies
-      parameters:
-      - description: Customer ID
-        in: path
-        name: id
-        required: true
-        type: string
-      produces:
-      - application/json
-      responses:
-        "200":
-          description: Customer retrieved successfully
-          schema:
-            allOf:
-            - $ref: '#/definitions/response.APIResponse'
-            - properties:
-                data:
-                  $ref: '#/definitions/customer.CustomerResponse'
-              type: object
-        "400":
-          description: Bad request - Invalid customer ID
-          schema:
-            $ref: '#/definitions/response.APIResponse'
-        "404":
-          description: Not found - Customer not found
-          schema:
-            $ref: '#/definitions/response.APIResponse'
-        "500":
-          description: Internal server error
-          schema:
-            $ref: '#/definitions/response.APIResponse'
-      security:
-      - BearerAuth: []
-      summary: Get customer by ID with companies
-      tags:
-      - Admin-Customers
   /admin/v1/customers/company/{companyId}:
     get:
       consumes: