feat: Archive tab — role-scoped list of archived tasks with search

New /archive page (nav link for all roles) backed by GET /api/v1/archive:
- admins see every archived task;
- consultants see archived tasks for customers they're assigned to;
- developers see archived tasks they were assigned to, claimed, or acted on.
Supports full-text ?q= search; cards link to the task detail view.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/http/web.go

@@ -246,6 +246,7 @@ func (s *Server) routesWeb(mux *http.ServeMux) {
 	rolePage("/consultant/reviews", "reviews.html", "Review Queue", "reviews", "/static/js/reviews.js", isCons)
 	rolePage("/consultant/pool", "pool.html", "Developer Pool", "pool", "/static/js/pool.js", isCons)
 	rolePage("/notifications", "notifications.html", "Notifications", "", "/static/js/notifications-page.js", nil)
+	rolePage("/archive", "archive.html", "Archive", "archive", "/static/js/archive.js", nil)
 
 	mux.HandleFunc("GET /tasks/{id}", s.page(func(w http.ResponseWriter, r *http.Request, u *domain.User) {
 		s.render(w, r, "task.html", &pageData{