Website: machine estimator v2 — fold-out categories and the memory bar (still unlisted, R-997)

Each category is a native <details>, closed at first, with an 'n selected' count;
a preset opens what it ticks. A sticky memory bar (0-64 GB, marks 8/16/24/32/48/64+):
solid fill = smallest box memory where the selection fits well, thin mark = where it
fits, but tight; one line names the box to buy. minBoxGb() inverts guestMib() by
bisection on it, so the rule is still written once. Box sizes 12/24/48/64 added;
tests cover seven sizes and the inverse (red-proofed); SIZING.md table gains 24 GB.

website/assets/sizing-data.json

@@ -18,9 +18,22 @@
  },
  "boxes_gb": [
   8,
+  12,
   16,
-  32
+  24,
+  32,
+  48,
+  64
  ],
+ "bar_marks_gb": [
+  8,
+  16,
+  24,
+  32,
+  48,
+  64
+ ],
+ "bar_max_gb": 64,
  "categories": [
   {
    "id": "fajlkezeles",