Polish the requester "My requests" page: a Content-menu link, action-button styling, and return-to-page after acting

Follow-up to #3611212 (the requester "My requests" page). Discoverability and behavior fixes found in use:

• Add a My Orchestra requests menu link under the Content admin menu, beside Orchestra tasks and My Orchestra actions, gated by the page's View own process instances permission, so a user finds the requests they started next to the work awaiting them.
• Style the requester's action on each card as a real button, scoped under the card so it wins over a theme's own .button rules (which otherwise left the label unstyled, and its text black on hover).
• Thread this page as the return target onto that action link (through the shared return helper), so completing an assigned step from here returns to the list rather than chaining to the workflow's next step.
• Remove stray version: lines from the module's libraries file.

Scope: the card surfaces a requester's assigned (work item) steps. An unassigned "modify by link" interaction step, reached by an emailed bearer link, is intentionally not surfaced here; doing so safely needs a stored recipient identity to match against the current user, left to a separate issue.

Kernel tests cover the menu link and the return threading; docs and French translations are updated.