fix v1.41.2: uploaded files survive marker rebinding

- new WS houseplan/files/migrate moves /files/<oldId>/ to the new id
  (admin-only, sanitized ids, merge-safe, removes the empty old dir)
- _saveMarker calls it and rewrites pdf urls (migratePdfUrls pure
  helper, +1 unit test, 112) when rebinding changes the id
- field incident: the sauna heater manuals pointed at an orphaned
  old-id folder that got cleaned up; data restored by hand on the
  home instance (official Harvia PDFs re-downloaded)
- TESTING/CHANGELOG same-commit

test/logic.test.mjs

@@ -10,6 +10,7 @@ import {
   outlineWithout,
   alignGuides, segmentAngle, is45,
   swipeTarget, clampScale,
+  migratePdfUrls,
   segmentCm, formatLength, roomEdges, roomPoly, pointOnBoundary, pointStrictlyInside, roomsOverlap,
   mergeRooms, splitRoom, polygonArea, closestPointOnBoundary, isActiveState, snapToWall, openingAmount, fillColorsOf, lerpColor, roomFillStyle, stateIcon, lightColorOf, isAlarmState, parseRoomRef, diffNewDevices,
 } from '../test-build/logic.js';
@@ -787,3 +788,15 @@ test('clampScale', () => {
   assert.equal(clampScale('x'), 1);
   assert.equal(clampScale(undefined, 1.5), 1.5);
 });
+
+test('migratePdfUrls: rebinding rewrites file urls', () => {
+  const pdfs = [
+    { name: 'a.pdf', url: '/houseplan_files/files/v_old1/a.pdf?v=1' },
+    { name: 'b.pdf', url: '/houseplan_files/files/other/b.pdf?v=2' },
+  ];
+  const out = migratePdfUrls(pdfs, 'v_old1', 'dev99');
+  assert.equal(out[0].url, '/houseplan_files/files/dev99/a.pdf?v=1');
+  assert.equal(out[1].url, pdfs[1].url); // чужие пути не трогаем
+  // без смены id — как есть
+  assert.equal(migratePdfUrls(pdfs, 'x', 'x'), pdfs);
+});