fix(launcher): use parent type_code for session_type, not per-file field

The event_session_type_code field on file objects is often null, causing
poster-mode files to fall back to 'oral' and render as download buttons
instead of modal openers.

- launcher_session_view: session-level files now use derived type_code
- launcher_presenter_view: add session_type prop (default 'oral'); parent passes type_code
- launcher_presenter_view_posters: hardcode poster/modal (only ever rendered in poster context)
- launcher_menu event/location files unchanged: no session context, field is the only signal

src/routes/events/[event_id]/(launcher)/launcher_session_view.svelte

@@ -300,12 +300,8 @@
                                 hide_created_on={true}
                                 show_bak_download={$ae_loc.trusted_access &&
                                     $ae_loc.edit_mode}
-                                session_type={event_file_obj?.event_session_type_code ??
-                                    'oral'}
-                                open_method={event_file_obj?.event_session_type_code ==
-                                'poster'
-                                    ? 'modal'
-                                    : null}
+                                session_type={type_code || 'oral'}
+                                open_method={type_code == 'poster' ? 'modal' : null}
                                 modal_title={$lq__event_session_obj?.name}
                                 bind:modal__title={
                                     $events_sess.launcher.modal__title
@@ -451,6 +447,7 @@
                                                 {:else}
                                                     <Launcher_presenter_view
                                                         lq__event_presenter_obj={event_presenter_obj}
+                                                        session_type={type_code}
                                                     />
                                                 {/if}
                                             </li>