Add pricing details for Claude Opus 4.5 model in billing management documentation

Author: raul-ink

docs/account-management/billing-management.mdx

@@ -99,6 +99,7 @@ For models that accept image input, pricing is based on text tokens.
 | Claude Sonnet 4   | $3.00                       | $15.00                       | 200k tokens      | High-performance version |
 | Claude Opus 4     | $15.00                      | $75.00                       | 200k tokens      | High-performance reasoning |
 | Claude Opus 4.1   | $15.00                      | $75.00                       | 200k tokens      | **Most capable model yet**, excels at complex reasoning & advanced coding |
+| Claude Opus 4.5   | $5.00                       | $25.00                       | 200k tokens      | Latest model with improved performance |
 
 <details>
 <summary> View Legacy Claude Models</summary>