feat: add animated number transitions to dashboard stats

Numbers smoothly count up/down when switching date ranges,
applying filters, or as real-time visitor count changes.
Uses framer-motion useSpring for natural spring physics.

components/ui/animated-number.tsx

@@ -0,0 +1,29 @@
+'use client'
+
+import { useEffect, useRef } from 'react'
+import { useMotionValue, useSpring, useTransform, motion } from 'framer-motion'
+
+interface AnimatedNumberProps {
+  value: number
+  format: (v: number) => string
+  className?: string
+}
+
+export function AnimatedNumber({ value, format, className }: AnimatedNumberProps) {
+  const motionValue = useMotionValue(value)
+  const spring = useSpring(motionValue, { stiffness: 120, damping: 20, mass: 0.5 })
+  const display = useTransform(spring, (v) => format(Math.round(v)))
+  const isFirst = useRef(true)
+
+  useEffect(() => {
+    if (isFirst.current) {
+      // Skip animation on initial render — jump straight to value
+      motionValue.jump(value)
+      isFirst.current = false
+    } else {
+      motionValue.set(value)
+    }
+  }, [value, motionValue])
+
+  return <motion.span className={className}>{display}</motion.span>
+}