Snackbars are hidden behind menus, dialogs and other panels

Notification messages appear underneath other parts of the interface, so the feedback the user is waiting for can be half-covered or completely invisible. With the main menu open, the notification at the bottom-left is cut in half by the menu panel, which reads as a broken message rather than a hidden one. With a configuration page, the video library, a context menu or the tutorial open, it is not visible at all, so an action can silently look like it did nothing.

To reproduce: open the main menu (or any settings page over it) and do something that reports back, for example applying a vehicle address or switching a map tile provider. The notification is drawn behind the panel.

Notifications are the only feedback channel for a lot of actions, so they should always be the topmost layer. Today `#snackbar-container` (`src/components/SnackbarContainer.vue:22`) sits at `z-index: 800`, below almost every other floating surface in the app: the main menu (1000 and 9999), Vuetify dialogs (2400 by default), `GlassModal` (2000/5000), the base-station panel (50000), the POI and base-station context popups (99999) and the tutorial (1000000).

Start at src/components/SnackbarContainer.vue:22 and reproduce the issue with the main menu, a configuration page, a context menu, or the tutorial open. Review the listed floating-surface layers and verify the snackbar remains fully visible above them while actions such as applying a vehicle address still report feedback. Done means notifications are not covered or hidden by these panels.

Written by the indexing model from the issue text.