Add Christmas theme and snow effects for December

Introduces a Christmas theme that activates in December, including themed colors, subtle background patterns, and snowflake effects on loading screens. Adds a reusable SnowLoader component and utility for December detection. Updates layout and loading components to conditionally apply decorations and styles only during December.

components/christmas-decorations.tsx

@@ -1,21 +1,31 @@
 "use client"
 
 import { useEffect, useState } from "react"
+import { isDecember } from "@/lib/utils/christmas"
 
 export function ChristmasDecorations() {
   const [snowflakes, setSnowflakes] = useState<Array<{ id: number; left: number; delay: number; duration: number }>>([])
+  const [isDec, setIsDec] = useState(false)
 
   useEffect(() => {
-    // Generate snowflakes
-    const flakes = Array.from({ length: 30 }, (_, i) => ({
-      id: i,
-      left: Math.random() * 100,
-      delay: Math.random() * 5,
-      duration: 8 + Math.random() * 4,
-    }))
-    setSnowflakes(flakes)
+    setIsDec(isDecember())
+    
+    if (isDecember()) {
+      // Generate snowflakes
+      const flakes = Array.from({ length: 30 }, (_, i) => ({
+        id: i,
+        left: Math.random() * 100,
+        delay: Math.random() * 5,
+        duration: 8 + Math.random() * 4,
+      }))
+      setSnowflakes(flakes)
+    }
   }, [])
 
+  if (!isDec) {
+    return null
+  }
+
   return (
     <div className="fixed inset-0 pointer-events-none z-50 overflow-hidden">
       {/* Snowflakes */}