Refactor UI imports and update component paths

Replaces imports from 'components/ui' with 'components/common' across the app and dashboard pages, and updates model and API imports to use new paths under 'lib'. Removes redundant authentication checks from several dashboard pages. Adds new dashboard components and utility files, and reorganizes hooks and services into the 'lib' directory for improved structure.

components/layout/theme-toggle.tsx

@@ -0,0 +1,30 @@
+"use client"
+
+import * as React from "react"
+import { Moon, Sun } from "lucide-react"
+import { useTheme } from "next-themes"
+
+export function ThemeToggle() {
+  const [mounted, setMounted] = React.useState(false)
+  const { theme, setTheme } = useTheme()
+
+  React.useEffect(() => {
+    setMounted(true)
+  }, [])
+
+  if (!mounted) {
+    return null
+  }
+
+  return (
+    <button
+      onClick={() => setTheme(theme === "dark" ? "light" : "dark")}
+      className="relative p-2 hover:bg-gray-100 dark:hover:bg-[#1F1F23] rounded-full transition-colors"
+    >
+      <Sun className="h-5 w-5 text-gray-600 dark:text-gray-300 transition-all dark:hidden" />
+      <Moon className="h-5 w-5 text-gray-600 dark:text-gray-300 transition-all hidden dark:block" />
+      <span className="sr-only">Toggle theme</span>
+    </button>
+  )
+}
+