fix: improve campaign stats, shared chart components, and i18n coverage

- Extract shared chart constants to constants/charts.ts
- Add TREND_STYLES to stats/constants.ts for reuse
- Fix useChartColors with MutationObserver for theme changes
- Fix DailyChart date parsing to prevent timezone shift
- Add truncate to StatCard value for overflow safety
- Fix CampaignCard copy feedback inside try block
- Add NaN validation and staleTime to AdminCampaignStats
- Replace hardcoded strings with i18n keys in Referral page
- Add missing i18n keys across all 4 locales (en, ru, zh, fa)
- Add sales stats route to AdminPanel and App router

src/constants/charts.ts

@@ -0,0 +1,22 @@
+export const CHART_COMMON = {
+  KOPEKS_DIVISOR: 100,
+  GRADIENT: {
+    START_OFFSET: '5%',
+    END_OFFSET: '95%',
+    START_OPACITY: 0.3,
+    END_OPACITY: 0,
+  },
+  AXIS: {
+    TICK_FONT_SIZE: 11,
+  },
+  TOOLTIP: {
+    BORDER_RADIUS: '8px',
+    FONT_SIZE: '12px',
+  },
+  STROKE_WIDTH: 2,
+  GRID_DASH: '3 3',
+  STALE_TIME: 60_000,
+  CHART: {
+    MARGIN: { top: 5, right: 10, left: 0, bottom: 5 },
+  },
+} as const;

src/constants/partner.ts

@@ -1,39 +1,33 @@
+import { CHART_COMMON } from './charts';
+
 export const PARTNER_STATS = {
   /** Chart visual configuration */
   CHART: {
+    ...CHART_COMMON.CHART,
     HEIGHT: 200,
-    MARGIN: { top: 5, right: 10, left: 0, bottom: 5 },
   },
   /** Kopeks-to-currency divisor */
-  KOPEKS_DIVISOR: 100,
+  KOPEKS_DIVISOR: CHART_COMMON.KOPEKS_DIVISOR,
   /** 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,
-  },
+  GRADIENT: CHART_COMMON.GRADIENT,
   /** Axis tick styling */
   AXIS: {
-    TICK_FONT_SIZE: 11,
+    TICK_FONT_SIZE: CHART_COMMON.AXIS.TICK_FONT_SIZE,
     EARNINGS_WIDTH: 45,
     REFERRALS_WIDTH: 30,
   },
   /** Tooltip styling */
-  TOOLTIP: {
-    BORDER_RADIUS: '8px',
-    FONT_SIZE: '12px',
-  },
+  TOOLTIP: CHART_COMMON.TOOLTIP,
   /** Area stroke width */
-  STROKE_WIDTH: 2,
+  STROKE_WIDTH: CHART_COMMON.STROKE_WIDTH,
   /** Grid dash array */
-  GRID_DASH: '3 3',
+  GRID_DASH: CHART_COMMON.GRID_DASH,
   /** 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,
+  STATS_STALE_TIME: CHART_COMMON.STALE_TIME,
 } as const;