feat: add Next Lesson widget and enhance existing widgets

- Implemented a new Next Lesson widget to display the upcoming lesson details on the home screen.
- Updated Today widget to dynamically adjust the number of lessons displayed based on available space.
- Enhanced the Settings screen to allow users to manage hidden lessons more effectively.
- Introduced harmonized color palettes for better visual consistency across themes.
- Updated the timetable API to support a new range parameter for semester-based queries.
- Added tests to ensure the new semester range functionality works as expected.
- Refactored widget styling for improved appearance on devices with different Android versions.

server/timetable.js

@@ -5,6 +5,9 @@ import { lessonKey, subgroupsOf } from "../shared/lessons.js";
 import { occurrence, peopleAndRooms, roomsOn } from "./directory.js";
 
 const MAX_DAYS = 62;
+// A whole semester with its session fits easily; the cap only guards against abuse.
+const MAX_SEMESTER_DAYS = 200;
+const DAY_MS = 86_400_000;
 
 function lessonOut(lesson, group, people, date, status, calendar) {
   const bell = calendar?.bells.find((b) => b.start === lesson.start);
@@ -33,13 +36,23 @@ function lessonOut(lesson, group, people, date, status, calendar) {
  * days: one entry per date from `from`, with the lessons that take place that day.
  * weekly: the Word rows by weekday, for when dates cannot be calculated.
  */
-export function timetable({ file, schedule, calendar, group, from, days }) {
+export function timetable({ file, schedule, calendar, group, from, days, range, today }) {
   if (!schedule.groups.includes(group)) {
     const error = new Error(`В документе нет группы ${group}.`);
     error.status = 404;
     throw error;
   }
-  const count = Math.min(Math.max(Number(days) || 7, 1), MAX_DAYS);
+  let count = Math.min(Math.max(Number(days) || 7, 1), MAX_DAYS);
+  // range=semester: every day of the semester `today` falls in, so a client can keep
+  // the whole term offline. Without a known semester it keeps the plain from/days window.
+  if (range === "semester") {
+    const current = semesterView(calendar, schedule, today || from);
+    if (current) {
+      from = current.semester.start;
+      const span = Math.round((Date.parse(current.semester.end) - Date.parse(from)) / DAY_MS) + 1;
+      count = Math.min(Math.max(span, 1), MAX_SEMESTER_DAYS);
+    }
+  }
   const lessons = schedule.lessons.filter((l) => l.groups.includes(group));
   const entries = lessons.map((lesson) => ({
     doc: { id: file.id, schedule },