feat: redesign day picker with expandable calendar, status markers & Playwright E2E testing

- Replace modal calendar with inline expandable calendar widget integrated into the day picker.
- Add status indicator dots (attended/absent/pending) to month calendar grid matching day picker.
- Disable and gray out weekend days in calendar when weekend schedule is turned off.
- Redesign extend bar with integrated handle that aligns with the palette.
- Remove start-to-end timing on Today screen's class time rail, showing only start time.
- Implement Playwright E2E and visual testing suite with multi-screen capture scripts.
- Add cascade DELETE endpoints for subjects and versioned recurring timetable entries.

scripts/serve-dist.mjs

@@ -0,0 +1,53 @@
+import { createServer } from 'node:http';
+import { readFileSync, existsSync, statSync } from 'node:fs';
+import { join, extname } from 'node:path';
+
+const PORT = 3000;
+const DIST = join(process.cwd(), 'dist-web');
+
+const MIME = {
+  '.html': 'text/html; charset=utf-8',
+  '.js': 'application/javascript; charset=utf-8',
+  '.css': 'text/css; charset=utf-8',
+  '.json': 'application/json; charset=utf-8',
+  '.png': 'image/png',
+  '.jpg': 'image/jpeg',
+  '.ico': 'image/x-icon',
+  '.svg': 'image/svg+xml',
+  '.ttf': 'font/ttf',
+  '.woff': 'font/woff',
+  '.woff2': 'font/woff2',
+};
+
+const server = createServer((req, res) => {
+  const url = new URL(req.url || '/', `http://localhost:${PORT}`);
+  let pathname = decodeURIComponent(url.pathname);
+  if (pathname === '/') pathname = '/index.html';
+  
+  let filePath = join(DIST, pathname);
+  if (!existsSync(filePath) || statSync(filePath).isDirectory()) {
+    if (existsSync(join(DIST, `${pathname}.html`))) {
+      filePath = join(DIST, `${pathname}.html`);
+    } else if (existsSync(join(filePath, 'index.html'))) {
+      filePath = join(filePath, 'index.html');
+    } else {
+      filePath = join(DIST, 'index.html');
+    }
+  }
+
+  const ext = extname(filePath);
+  const contentType = MIME[ext] || 'application/octet-stream';
+
+  try {
+    const data = readFileSync(filePath);
+    res.writeHead(200, { 'Content-Type': contentType });
+    res.end(data);
+  } catch (err) {
+    res.writeHead(404);
+    res.end('Not found');
+  }
+});
+
+server.listen(PORT, '127.0.0.1', () => {
+  console.log(`Static server running at http://127.0.0.1:${PORT}`);
+});