fix: scope IssueBulkUpdateDateEndpoint query to workspace and project (#8834)

The bulk update date endpoint fetched issues by ID without filtering
by workspace or project, allowing any authenticated project member to
modify start_date and target_date of issues in any workspace/project
across the entire instance (IDOR - CWE-639).

Scoped the query to include workspace__slug and project_id filters,
consistent with other issue endpoints in the codebase.

Ref: GHSA-4q54-h4x9-m329