refactor: consolidate utilities, clean up components, and improve theme persistence

- Consolidate common utilities (cn, format, time) into lib/utils
- Remove redundant utility files from pastel and units directories
- Clean up unused components (Separator, KeyboardShortcutsHelp)
- Relocate CommandPalette to components/units/ui/
- Force dark mode on landing page and improve theme persistence logic
- Add FOUC prevention script to RootLayout
- Fix sidebar height constraint in AppShell

lib/pastel/utils/cn.ts

@@ -1,6 +0,0 @@
-import { clsx, type ClassValue } from 'clsx';
-import { twMerge } from 'tailwind-merge';
-
-export function cn(...inputs: ClassValue[]) {
-  return twMerge(clsx(inputs));
-}

lib/utils/format.ts

@@ -1,17 +1,3 @@
-/**
- * Utility functions for the application
- */
-
-import { type ClassValue, clsx } from 'clsx';
-import { twMerge } from 'tailwind-merge';
-
-/**
- * Merge Tailwind CSS classes with clsx
- */
-export function cn(...inputs: ClassValue[]) {
-  return twMerge(clsx(inputs));
-}
-
 /**
  * Format a number for display with proper precision
  */
@@ -53,26 +39,6 @@ export function formatNumber(
   return formatted;
 }
 
-/**
- * Debounce function for input handling
- */
-export function debounce<T extends (...args: any[]) => any>(
-  func: T,
-  wait: number
-): (...args: Parameters<T>) => void {
-  let timeout: NodeJS.Timeout | null = null;
-
-  return function executedFunction(...args: Parameters<T>) {
-    const later = () => {
-      timeout = null;
-      func(...args);
-    };
-
-    if (timeout) clearTimeout(timeout);
-    timeout = setTimeout(later, wait);
-  };
-}
-
 /**
  * Parse a number input string
  */
@@ -86,21 +52,3 @@ export function parseNumberInput(input: string): number | null {
 
   return isNaN(parsed) ? null : parsed;
 }
-
-/**
- * Get relative time from timestamp
- */
-export function getRelativeTime(timestamp: number): string {
-  const now = Date.now();
-  const diff = now - timestamp;
-
-  const seconds = Math.floor(diff / 1000);
-  const minutes = Math.floor(seconds / 60);
-  const hours = Math.floor(minutes / 60);
-  const days = Math.floor(hours / 24);
-
-  if (days > 0) return `${days}d ago`;
-  if (hours > 0) return `${hours}h ago`;
-  if (minutes > 0) return `${minutes}m ago`;
-  return 'just now';
-}

lib/utils/index.ts

@@ -2,3 +2,5 @@ export * from './cn';
 export * from './debounce';
 export * from './urlSharing';
 export * from './animations';
+export * from './format';
+export * from './time';

lib/utils/time.ts

@@ -0,0 +1,17 @@
+/**
+ * Get relative time from timestamp
+ */
+export function getRelativeTime(timestamp: number): string {
+  const now = Date.now();
+  const diff = now - timestamp;
+
+  const seconds = Math.floor(diff / 1000);
+  const minutes = Math.floor(seconds / 60);
+  const hours = Math.floor(minutes / 60);
+  const days = Math.floor(hours / 24);
+
+  if (days > 0) return `${days}d ago`;
+  if (hours > 0) return `${hours}h ago`;
+  if (minutes > 0) return `${minutes}m ago`;
+  return 'just now';
+}