Support pageStart in x-pagination extension

Add support for the pageStart field in the x-pagination OpenAPI extension
to allow APIs that use 1-based page numbering (like Case Management) to
work correctly with pagination helpers.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: amaskara-dd

.generator/src/generator/templates/Api.j2

@@ -148,7 +148,7 @@ public class {{ name }} {
   String valueGetterPath = "";
   String valueSetterPath = "{%- if getters|length > 1 %}{{ ".".join(getters[:getters|length-1]) }}.{%- endif %}{{ setters[getters|length-1] }}";
   Boolean valueSetterParamOptional = {{ optional|lower }};
-  parameters.{% if getters|length > 1 %}{{ ".".join(getters[:getters|length-1]) }}.{%- endif %}{{ setters[getters|length-1] }}({{ 0|format_value(schema=paramSchema['schema']) }});
+  parameters.{% if getters|length > 1 %}{{ ".".join(getters[:getters|length-1]) }}.{%- endif %}{{ setters[getters|length-1] }}({{ (pagination.pageStart | default(0))|format_value(schema=paramSchema['schema']) }});
   {%- endif %}
 
 {#- Limit param field #}