feat(notifications): show full notification details with actions

Long announcements were clamped in the list and had nowhere to open, so
notifications now open a detail dialog with the full message, type, theme,
sender and timestamp, plus a shortcut into the Community Workshop.

src/lib/notifications.ts

@@ -16,6 +16,7 @@ export interface UserNotification {
   themeId: string | null;
   themeName: string | null;
   actorId: number | null;
+  actorName?: string | null;
   readAt: string | null;
   createdAt: string;
 }