fix(apps): bump --app-min from 300 to 328 so typical laptops drop to 2 cols and stop orphaning

User's empirical fix: on a 1280-class viewport (sidebar 220, content
~1010), --app-min 300 made the grid pick 3 cols because
floor((1010+20)/(300+20)) = 3, which left a 4-card category landing
as 3+1 with the orphan-row gap that's been the running visual
complaint. Bumping --app-min to 328 changes the floor to
floor((1010+20)/(328+20)) = 2, so the same 4-card category becomes
2+2 with no orphan.

Wider monitors are unaffected — a 1056px content area still fits 3
tracks of 328 (3*328 + 2*20 = 1024 ≤ 1056), and 1700px+ content
still fits 4. The cards-per-row count only drops on the narrow band
where 300 would otherwise have squeezed a third just-too-tight
column in.

Signed-off-by: librelad <librelad@digitalangels.vip>

containers/libreportal/frontend/css/apps.css

@@ -3,7 +3,14 @@
 /* App center cards, grid, tags, and detail view. Extracted from style.css. */
 
 .apps-section {
-  --app-min: 300px;
+  /* Track min-width is the lever for "how many columns at this viewport".
+     auto-fill picks floor((content + gap) / (--app-min + gap)) tracks, so
+     bumping --app-min from 300 to 328 pushes typical 1280px-class laptops
+     from 3 cols → 2 cols where the third column would have been the
+     orphan that ran into a half-empty last row. Wider monitors still hit
+     3+ cols (e.g. 1056px content fits 3 tracks of 328 with room to
+     spare), so density on bigger screens is unchanged. */
+  --app-min: 328px;
   --app-gap: 20px;
   display: grid;
   /* Fixed-width tracks so cards stay exactly --app-min wide regardless