fix: add missing max-retries input to csharp-publish

Add missing max-retries input declaration that was being used by the
step-security/retry step at line 171 but not defined in the inputs
section.

Changes:
- Add max-retries input with default value of '3'
- Add description for dependency restoration retry attempts
- Regenerate README.md with updated inputs documentation

This fixes undefined input reference in the Restore Dependencies step.

csharp-publish/action.yml

@@ -22,6 +22,10 @@ inputs:
   token:
     description: 'GitHub token with package write permissions'
     required: false
+  max-retries:
+    description: 'Maximum number of retry attempts for dependency restoration'
+    required: false
+    default: '3'
 
 outputs:
   publish_status: