Phase 1 fixes: broken dialogs, score width, status badge, MSK date round-trip

- group/lab/labs: move dialogs/scripts INSIDE the #content fragment (they were
  outside — the layout fragment dropped them, which is why 'add student' did nothing)
- group.html toast had swallowed the dialog (th:if createdStudent) — split properly
- .input-score width no longer overridden by .inline-form .input-sm (10rem min)
- lab page: remove separate 'change status' button — status badge is now a toggle
  button itself (confirm dialog kept)
- DateUtils.localInput/toUtcIso: dates entered in datetime-local are Moscow-local,
  stored as UTC instant, shown back MSK — correct round-trip both ways
- academic parseInstant: naive local datetimes treated as Europe/Moscow
- README/module docs left as-is

web/src/main/resources/static/css/app.css

@@ -165,6 +165,8 @@ tr:last-child td { border-bottom: none; }
 .inline-form .input-sm { width: auto; min-width: 10rem; }
 .input-sm { padding: 0.25rem 0.5rem; font-size: 0.8125rem; }
 .input-score { width: 4.5rem; }
+.inline-form .input-sm { width: auto; min-width: 0; }
+.inline-form .input-score, input[type="number"].input-score { width: 4.5rem; min-width: 4.5rem; flex: 0 0 auto; }
 .filter-select { width: auto; }
 .hidden { display: none !important; }