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/store/endpoints.go

@@ -19,6 +19,13 @@ func (s *Store) CreateEndpoint(ctx context.Context, e Endpoint) (int64, error) {
 	return id, err
 }
 
+func (s *Store) UpdateEndpoint(ctx context.Context, e Endpoint) error {
+	_, err := s.Pool.Exec(ctx,
+		`UPDATE endpoints SET role_label=$2, host=$3, port=$4, tls_mode=$5 WHERE id=$1`,
+		e.ID, e.RoleLabel, e.Host, e.Port, e.TLSMode)
+	return err
+}
+
 func (s *Store) GetEndpoint(ctx context.Context, id int64) (Endpoint, error) {
 	var e Endpoint
 	err := s.Pool.QueryRow(ctx,