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/constants/partner.ts

@@ -0,0 +1,39 @@
+export const PARTNER_STATS = {
+  /** Chart visual configuration */
+  CHART: {
+    HEIGHT: 200,
+    MARGIN: { top: 5, right: 10, left: 0, bottom: 5 },
+  },
+  /** Kopeks-to-currency divisor */
+  KOPEKS_DIVISOR: 100,
+  /** Copy feedback duration in ms */
+  COPY_FEEDBACK_MS: 2000,
+  /** Gradient stop offsets */
+  GRADIENT: {
+    START_OFFSET: '5%',
+    END_OFFSET: '95%',
+    START_OPACITY: 0.3,
+    END_OPACITY: 0,
+  },
+  /** Axis tick styling */
+  AXIS: {
+    TICK_FONT_SIZE: 11,
+    EARNINGS_WIDTH: 45,
+    REFERRALS_WIDTH: 30,
+  },
+  /** Tooltip styling */
+  TOOLTIP: {
+    BORDER_RADIUS: '8px',
+    FONT_SIZE: '12px',
+  },
+  /** Area stroke width */
+  STROKE_WIDTH: 2,
+  /** Grid dash array */
+  GRID_DASH: '3 3',
+  /** Skeleton count for loading state */
+  SKELETON_COUNT: 3,
+  /** Maximum conversion rate for progress bar */
+  MAX_CONVERSION_RATE: 100,
+  /** Stale time for campaign stats query (ms) */
+  STATS_STALE_TIME: 60_000,
+} as const;