feat: Add skeleton loading UI components for various screens

- Implemented `Skeleton.kt` for loading placeholders in the app, including lesson cards, schedule, overview, and subjects.
- Introduced `Undo.kt` to manage undo actions with a snackbar interface.
- Created `WeekWidget.kt` for a widget displaying the week's schedule, including dynamic updates based on the current timetable.
- Added various splash animations in the `animator` directory for a smooth launch experience.
- Designed drawable resources for the widget and splash screen, including icons for city and room moves.
- Defined XML resources for widget configuration and photo paths.

scripts/snapshot-lines.js

@@ -15,7 +15,11 @@ export const lessonLine = (l) =>
     // The town only when the cell names one or the day's note puts the lesson there.
     [l.room, l.place].filter(Boolean).join(", "),
     l.teacher,
-    [...l.groups, ...l.subgroups.map((s) => `${s.group}/${s.label.replace("Подгруппа ", "п")}`)].join(","),
+    [...l.groups, ...l.subgroups.map((s) => `${s.group}/${s.label.replace("Подгруппа ", "п")}`)].join(",") +
+      // "Немецкий язык" or "Французский язык": a part of the group takes one of them.
+      (l.option ? " · на выбор" : "") +
+      // Russian for foreign students while the others have physical education.
+      (l.audience === "foreign" ? " · иностранцам" : l.audience === "local" ? " · кроме иностранцев" : ""),
   ]
     .map((part) => String(part ?? "").replace(/\s+/g, " ").trim())
     .join(" | ");