feat(redesign): collapsible dashboard sections + glass mobile-more sheet

Generalize dashboard panel expansion: Stream / On Watch / Pulse / Wires
each get a chevron toggle persisted in localStorage under
dashboard_section_state (migrates legacy dashboard_chart_visible). Drop
the redundant inner border on EventChart so it doesn't double-frame the
panel. Mobile "more" sheet becomes full-height with translucent glass
(rgba(...,0.72) + 28px blur) instead of nearly-solid.

frontend/src/lib/components/EventChart.svelte

@@ -143,16 +143,12 @@
 
 <style>
 	.chart-wrapper {
-		background: var(--color-card);
-		border: 1px solid var(--color-border);
-		border-radius: 0.75rem;
-		padding: 1.25rem;
-		margin-bottom: 1.5rem;
-		transition: border-color 0.2s;
-	}
-	.chart-wrapper:hover {
-		border-color: var(--color-primary);
-		box-shadow: 0 0 16px var(--color-glow);
+		/* Outer chrome lives on the parent panel — keep this transparent so
+		   we don't get a double border / nested card look. */
+		background: transparent;
+		border: 0;
+		padding: 0;
+		margin-bottom: 0;
 	}
 	.chart-header {
 		display: flex;