Refactors date and file formatting utilities

refactor(utils): consolidate date and file size formatting

Extracts formatting logic into dedicated utility functions to improve
code maintainability and consistency across components.

Changes:
- Consolidate date formatting functions (formatRelativeTime, etc.)
- Consolidate file size formatting into single formatFileSize utility
- Fix file size calculation errors
- Update UI components to use new utilities
- Change "ASAP" to "Waiting" for unscheduled queue items

Tests:
- Add comprehensive unit tests for date utilities
- Add unit tests for file size formatting

frontend/src/utils/file.ts

@@ -0,0 +1,21 @@
+
+/**
+ * Formats a byte count into a human-readable string (e.g. `1.5 MB`).
+ *
+ * @param bytes - The number of bytes to format.
+ * @returns A formatted string with the appropriate unit (B, KB, MB, GB, or TB).
+ */
+export function formatFileSize(bytes: number): string {
+  if (bytes === 0) return '0 B';
+  
+  const units = ['B', 'KB', 'MB', 'GB', 'TB'];
+  const k = 1024;
+  const i = Math.floor(Math.log(bytes) / Math.log(k));
+  
+  const size = bytes / Math.pow(k, i);
+  
+  // No decimals for bytes, 1 decimal for larger units
+  return i === 0 
+    ? `${size} ${units[i]}` 
+    : `${size.toFixed(1)} ${units[i]}`;
+}