p2 layout

- _tokens.scss — added --wg-space-2xs…xl (0.25–2rem, 4pt scale), --wg-ledger-line: 1.78rem, --wg-page-width: 1420px.
- Card gaps unified to --wg-space-sm, card interiors to --wg-space-md, the compact topic-list header to --wg-space-xs (_categories.scss, _topics.scss, _widgets.scss, _responsive.scss).
- Ledger ruling height is now one token across topics, posts, pagination, quick-reply, and the composer (_posts.scss, _controls.scss).
- Footer rails now share the topbar's 1420px measure (_footer.scss:36,123,143), so the page's top and bottom edges align.
- Stat tiles got explicit padding instead of inheriting Bootstrap's (_topics.scss:369, _categories.scss:326).
- Documented the scale and rules in DESIGN.md (new "Spacing & Layout" section).

scss/westgate/_categories.scss

@@ -7,7 +7,7 @@ ul.categories-list,
 ul.westgate-categories-list {
   position: relative;
   display: grid;
-  gap: 0.75rem;
+  gap: var(--wg-space-sm);
   padding-left: 0;
 }
 
@@ -15,7 +15,7 @@ li[component="categories/category"] {
   position: relative;
   isolation: isolate;
   margin: 0 !important;
-  padding: 1rem !important;
+  padding: var(--wg-space-md) !important;
   overflow: visible;
   transition:
     background 0.18s ease,
@@ -323,6 +323,7 @@ ul.category-children {
 
 li[component="categories/category"] .meta.stats > div {
   min-height: 3.55rem;
+  padding: var(--wg-space-2xs) var(--wg-space-xs);
   background: rgba(255, 255, 255, 0.018) !important;
   border: 1px solid rgba(194, 163, 90, 0.09) !important;
   border-radius: 3px !important;