style(insights): tighten mood chart heights and unify the overview rhythm

The mood line chart plots a 1-5 score band; the 240/280 px full-mode height
left a dead strip below the line on the mood subpage. Trim the default to
200/220 px (a per-mount --chart-height override still wins) and lower the
mood-correlation scatter height so the cards fit their content without the
empty gap.

The overview used space-y-8 between top-level blocks while the vitals wrap used
space-y-6, reading as two tiers. Unify to space-y-6 for one consistent vertical
rhythm down the page, in line with the denser-Insights direction.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/insights/mood/mood-correlation-cards.tsx

@@ -128,7 +128,7 @@ function MoodCorrelationCard({
                 ticks: [1, 2, 3, 4, 5],
               }}
               yAxis={{ dataKey: "y", name: t(Y_LABEL_KEY[kind]) }}
-              height={180}
+              height={160}
             />
           </>
         ) : (