polish: fix page title, multi-select styling, chart colors

- Page title: "HiHala Data - Museums" -> "HiHala Data"
- Meta description: updated to "Event analytics"
- Multi-select dropdown: fix inherited uppercase, wider to fit labels
- Multi-select arrow: smooth CSS rotation instead of swapping characters
- Chart colors: 10-color palette for events/channels (was 3)
- Remove unused ArcElement (Doughnut) from Chart.js registration (-5KB)
- District chart uses dynamic palette instead of hardcoded 2 colors

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/config/chartConfig.ts

@@ -5,7 +5,7 @@ import {
   PointElement,
   LineElement,
   BarElement,
-  ArcElement,
+
   Title,
   Tooltip,
   Legend,
@@ -20,7 +20,7 @@ ChartJS.register(
   PointElement,
   LineElement,
   BarElement,
-  ArcElement,
+
   Title,
   Tooltip,
   Legend,
@@ -38,6 +38,20 @@ export const chartColors = {
   grid: '#f1f5f9'
 };
 
+// Extended palette for charts with many categories (events, channels)
+export const chartPalette = [
+  '#2563eb', // blue
+  '#7c3aed', // purple
+  '#0891b2', // cyan
+  '#059669', // emerald
+  '#d97706', // amber
+  '#e11d48', // rose
+  '#4f46e5', // indigo
+  '#0d9488', // teal
+  '#c026d3', // fuchsia
+  '#ea580c', // orange
+];
+
 export const createDataLabelConfig = (showDataLabels: boolean): any => ({
   display: showDataLabels,
   color: '#1e293b',