The /events Project filter dropdown was sorted by `updated_at DESC`, so a
recently-touched Case appeared above its parent Client and cousins
interleaved unrelated branches — m's report (2026-05-04): "Siemens cases
come directly after 'mandant vs Gegner' and are not under 'Siemens-AG'".
Backend: switch ProjectService.List to ORDER BY p.path so every
descendant immediately follows its ancestor — the same ordering BuildTree
produces. Both callers (handleListProjects, searchProjects) gain a
stable, hierarchical default that matches user expectation.
Frontend: add project-indent.ts shared helper and apply NBSP indent
prefix in every <select> picker fed by /api/projects: events filter,
/deadlines/new, /appointments/new, checklist new-instance modal,
Fristenrechner save modal. NBSP avoids browser whitespace collapse
inside <option> labels. Multi-parent repetition is out of scope (data
model has singular parent_id today).
Tests: project_list_order_test pins the path-order contract against a
seeded mixed-recency tree.
