Reduce hour-of-week heatmap cell size by 20%

CELL_SIZE 21->17, CELL_GAP 3->2, ROW_LABEL_WIDTH 36->29,
COL_LABEL_HEIGHT 22->18.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: wesm

frontend/src/lib/components/analytics/HourOfWeekHeatmap.svelte

@@ -1,11 +1,11 @@
 <script lang="ts">
   import { analytics } from "../../stores/analytics.svelte.js";
 
-  const CELL_SIZE = 21;
-  const CELL_GAP = 3;
+  const CELL_SIZE = 17;
+  const CELL_GAP = 2;
   const CELL_STEP = CELL_SIZE + CELL_GAP;
-  const ROW_LABEL_WIDTH = 36;
-  const COL_LABEL_HEIGHT = 22;
+  const ROW_LABEL_WIDTH = 29;
+  const COL_LABEL_HEIGHT = 18;
   const DAY_LABELS = [
     "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun",
   ];