[feature]: Add project member management (POST/PATCH/DELETE) to REST API v1

Is there an existing issue for this? • I have searched the existing issues Summary The current REST API v1 only exposes GET /api/v1/workspaces/{slug}/projects/{project_id}/members/ for reading project members. There is no endpoint to add, update, or remove project members via the API. These operations work fine through the web UI (which uses internal session-based endpoints), but are not available to API key / Personal Access Token consumers. This makes it impossible to automate member management across projects. Requested endpoints POST /api/v1/workspaces/{slug}/projects/{project_id}/members/ PATCH /api/v1/workspaces/{slug}/projects/{project_id}/members/{member_id}/ DELETE /api/v1/workspaces/{slug}/projects/{project_id}/members/{member_id}/ Why should this be worked on? Teams managing many projects need to automate member assignments. For example, when onboarding a new team member, a workspace admin should be able to programmatically add them to all (or a subset of) pr…