feat: Konsole parity phase 1b (layout save/load, SSH bookmarks)

- Serialize pane grid splits and per-tab state to RON
- Save/load layout via cosmic-files dialogs with confirmation
- SSH submenu from ~/.ssh/config Host entries (no wildcards)
- i18n en/fr for layout and SSH menu entries

i18n/en/cosmic_term.ftl

@@ -115,6 +115,12 @@ new-tab = New tab
 new-window = New window
 profile = Profile
 menu-profiles = Profiles...
+ssh = SSH
+save-layout = Save layout...
+load-layout = Load layout...
+load-layout-title = Load layout
+load-layout-body = Loading a layout replaces all tabs and splits in this window.
+load = Load
 close-tab = Close tab
 quit = Quit