feat: add recharts analytics to admin campaign stats page

- Move shared chart components (DailyChart, PeriodComparison, StatCard) to src/components/stats/ with configurable label props
- Create shared types for chart data decoupled from partner API
- Add campaign chart data API client with deposits/spending split
- Enhance AdminCampaignStats with daily trends chart, period comparison, top registrations, and deposit/spending stat cards
- Add useChartColors hook with SSR guard and theme-aware CSS variable parsing
- Add cross-platform clipboard utility with execCommand fallback for Telegram WebView
- Add i18n keys for chart analytics across all 4 locales (en, ru, zh, fa)
- Responsive fixes: truncation for long names/values, responsive text sizing, touch-friendly copy buttons

src/utils/clipboard.ts

@@ -0,0 +1,24 @@
+/**
+ * Cross-platform clipboard utility with fallback for Telegram WebView.
+ * navigator.clipboard.writeText() is unavailable in some WebViews
+ * (Android System WebView, unfocused tabs, insecure contexts).
+ */
+export async function copyToClipboard(text: string): Promise<void> {
+  try {
+    await navigator.clipboard.writeText(text);
+  } catch {
+    const textarea = document.createElement('textarea');
+    textarea.value = text;
+    textarea.style.position = 'fixed';
+    textarea.style.opacity = '0';
+    textarea.style.left = '-9999px';
+    document.body.appendChild(textarea);
+    try {
+      textarea.select();
+      const ok = document.execCommand('copy');
+      if (!ok) throw new Error('execCommand copy failed');
+    } finally {
+      document.body.removeChild(textarea);
+    }
+  }
+}