Requester-facing list of a user's own process instances: a "my requests" page and a "my workflow instances" View

Following #3611190 (record the initiator) and #3611204 (surface it in the admin list and Views), this adds the requester-facing side: a logged-in user sees the requests they started, with each one's status and current step, and no operator permission.

Two interchangeable surfaces, both scoped to the current user's initiator and the acting tenant, gated by a new View own process instances permission:

• orchestra_ui: a themed card page at /orchestra/my-requests (workflow title, reference, created date, status badge, current step, and a link to act when the requester has an open step of their own).
• orchestra_views: a shipped example My workflow instances View at /orchestra/my-instances (Reference, Workflow, Status, Current step, Created), living in the dedicated Views submodule as a template a site can clone for its own requester list.

Supporting pieces, reusable on their own:

• An orchestra.current_step_resolver service resolving a running instance's parked non-timer tokens to their version-pinned node labels, so a page and a View report the same step.
• A Current step Views field on the instance, backed by that service.

A read-only "view detail" affordance is intentionally left out of this MVP: per-request detail is source-specific (a Webform submission, a booking) and is a follow-up. Kernel tests cover the resolver, the page and the shipped View; docs and French translations are included.