feat: migrate from <GlobalSnackbar /> to sonner (#22258)

Replaces our custom `<GlobalSnackbar />` (MUI Snackbar + event emitter)
with [`sonner`](https://github.com/emilkowalski/sonner). Deletes
`GlobalSnackbar/`, the custom event emitter infra, and migrates ~80
source files to `toast.success()` / `toast.error()` from `sonner`.

- ~47 error toasts now surface API error detail via
`getErrorDetail(error)` in the toast description, not just a generic
message. Coincides with #22229.
- Toast messages follow an `{Action} "{entity}" {result}.` format (e.g.
`User "alice" suspended successfully.`) since toasts persist across
navigation now.
- 17 uses of `toast.promise()` for loading → success → error lifecycle.
- Some toasts include action buttons for quick navigation (e.g. "View
task", "View template").
- Multiple toasts can stack and display simultaneously.

---------

Co-authored-by: Kayla はな <mckayla@hey.com>

site/src/contexts/auth/AuthProvider.tsx

@@ -8,7 +8,6 @@ import {
 	updateProfile as updateProfileOptions,
 } from "api/queries/users";
 import type { UpdateUserProfileRequest, User } from "api/typesGenerated";
-import { displaySuccess } from "components/GlobalSnackbar/utils";
 import { useEmbeddedMetadata } from "hooks/useEmbeddedMetadata";
 import { type Permissions, permissionChecks } from "modules/permissions";
 import {
@@ -19,6 +18,7 @@ import {
 	useContext,
 } from "react";
 import { useMutation, useQuery, useQueryClient } from "react-query";
+import { toast } from "sonner";
 
 export type AuthContextValue = {
 	isLoading: boolean;
@@ -64,7 +64,6 @@ export const AuthProvider: FC<PropsWithChildren> = ({ children }) => {
 		...updateProfileOptions("me"),
 		onSuccess: (user) => {
 			queryClient.setQueryData(meOptions.queryKey, user);
-			displaySuccess("Updated settings.");
 		},
 	});
 
@@ -96,7 +95,12 @@ export const AuthProvider: FC<PropsWithChildren> = ({ children }) => {
 
 	const updateProfile = useCallback(
 		(req: UpdateUserProfileRequest) => {
-			updateProfileMutation.mutate(req);
+			const mutation = updateProfileMutation.mutateAsync(req);
+			toast.promise(mutation, {
+				loading: "Updating profile...",
+				success: "Profile updated successfully.",
+				error: "Failed to update profile.",
+			});
 		},
 		[updateProfileMutation],
 	);