feat(insights): rename "Muster" + lift section tabs above the hero

Two related polishing changes for the Insights surface:

a) Correlation row title rename. "Muster" / "Patterns" reads as a
   loose grouping; the row actually shows pre-defined statistical
   relationships between two metrics. Rename to "Zusammenhänge" /
   "Relationships" so the title carries the same conceptual weight as
   the surrounding "Trends" / "Daily Briefing" headers without
   borrowing the "Trends" word from the row above it. Picked
   "Zusammenhänge" over "Trends" because the Trends row already uses
   that word and a correlation is conceptually a relationship between
   two series rather than a single-series trend.

b) Section tabs lift above the hero strip. `<InsightsSectionNav>` was
   mounted below the advisor card so the user had to scroll past the
   hero before discovering the metric-tab nav. Lift it to the top of
   the page so the tabs are the first thing visible — the hero +
   daily briefing render directly below, and clicking a tab still
   scrolls to the matching section. Sticky scroll-anchored behaviour
   preserved (incremental over a full SPA-tab rewrite) so today's
   reactive surface keeps working.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/insights/__tests__/correlation-card.test.tsx

@@ -88,7 +88,7 @@ describe("<CorrelationCard>", () => {
 
   it("renders the empty-state when status=insufficient", () => {
     const html = render(<CorrelationCard result={insufficient} />);
-    expect(html).toContain("Need more data to see this pattern");
+    expect(html).toContain("Need more data to see this relationship");
     expect(html).not.toContain("Try a 7-day experiment");
   });
 

src/components/insights/__tests__/correlation-row.test.tsx

@@ -100,7 +100,7 @@ describe("<CorrelationRow>", () => {
     );
     const matches = html.match(/data-slot="correlation-row-disclaimer"/g) ?? [];
     expect(matches.length).toBe(1);
-    expect(html).toContain("Patterns are observational, not causal");
+    expect(html).toContain("Relationships are observational, not causal");
   });
 
   it("applies the 2-up grid on >= md when 2+ ok cards render", () => {