feat: delete task/account, edit endpoint, richer event log

- store: DeleteAccount, DeleteTask, UpdateEndpoint (+ cascade/update tests)
- httpapi: DELETE /tasks/{id}, DELETE /tasks/{id}/accounts/{accountId},
  PUT /endpoints/{id}; delete guarded with 409 while task running
- orchestrator: enrich WS events with login/host/port/error (test + run + errors)
- web: delete buttons (task, account) with confirm, endpoint edit form,
  human-readable event log (source/dest, host:port, error text)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMHQTtnQtQqL8muAXHr9kd

internal/httpapi/run.go

@@ -84,3 +84,52 @@ func (s *Server) handleRun(w http.ResponseWriter, r *http.Request) {
 	}
 	writeJSON(w, http.StatusAccepted, map[string]int64{"run_id": runID})
 }
+
+func (s *Server) handleDeleteTask(w http.ResponseWriter, r *http.Request) {
+	id, err := pathID(r, "id")
+	if err != nil {
+		http.Error(w, "bad id", http.StatusBadRequest)
+		return
+	}
+	task, err := s.store.GetTask(r.Context(), id)
+	if err != nil {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+	if task.Status == "running" {
+		http.Error(w, "cannot delete a running task", http.StatusConflict)
+		return
+	}
+	if err := s.store.DeleteTask(r.Context(), id); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (s *Server) handleDeleteAccount(w http.ResponseWriter, r *http.Request) {
+	taskID, err := pathID(r, "id")
+	if err != nil {
+		http.Error(w, "bad id", http.StatusBadRequest)
+		return
+	}
+	accID, err := pathID(r, "accountId")
+	if err != nil {
+		http.Error(w, "bad account id", http.StatusBadRequest)
+		return
+	}
+	task, err := s.store.GetTask(r.Context(), taskID)
+	if err != nil {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+	if task.Status == "running" {
+		http.Error(w, "cannot modify accounts while task is running", http.StatusConflict)
+		return
+	}
+	if err := s.store.DeleteAccount(r.Context(), accID); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}