docs: Update cost center page URL and add current month preview note (#608)

Author: muhsinking

accounts-billing/cost-centers.mdx

@@ -32,7 +32,7 @@ Each resource can belong to only one cost center at a time. Resources without an
 
 To create a new cost center:
 
-1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/tags) in the Runpod console.
+1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/manage) in the Runpod console.
 2. Select **Add a new cost center**.
 3. Enter a name for the cost center.
 4. Select **Create cost center** to confirm.
@@ -49,7 +49,7 @@ Resources are added to cost centers from the Cost center page. You can assign mu
 
 To add uncategorized resources to a cost center:
 
-1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/tags).
+1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/manage).
 2. Scroll to the **Uncategorized resources** section.
 3. Use the tabs to filter by resource type (Pods, Serverless Endpoints, Storage Volumes, or Instant Clusters) if needed.
 4. Select the checkbox next to each resource you want to assign.
@@ -71,7 +71,7 @@ To maintain accurate cost attribution:
 
 To rename a cost center:
 
-1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/tags).
+1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/manage).
 2. Locate the cost center you want to edit.
 3. Select the edit icon next to the cost center name.
 4. Enter the new name and confirm the change.
@@ -82,7 +82,7 @@ Renaming a cost center updates its name across the console and on future invoice
 
 To delete a cost center:
 
-1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/tags).
+1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/manage).
 2. Locate the cost center you want to delete.
 3. Select the delete icon next to the cost center name.
 4. Confirm the deletion.
@@ -97,11 +97,15 @@ Deleting a cost center moves all its assigned resources to the uncategorized lis
 Invoices may take up to 60 minutes to reflect new spending data.
 </Note>
 
+<Note>
+The current month's invoice is a preview and does not have a downloadable PDF. A downloadable PDF becomes available after the billing month closes.
+</Note>
+
 Your Runpod invoices include a breakdown of total spend by cost center. Invoices show how charges are distributed across your organization's cost centers.
 
 To view invoices with cost center data:
 
-1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/tags).
+1. Navigate to the [Cost center page](https://www.console.runpod.io/user/cost-center/manage).
 2. Select the **Invoices** tab.
 
 Each invoice shows the total amount spent per cost center in a given month, making it easy to allocate charges to the appropriate teams or budgets in your financial systems.