Add packages/common for shared utilities

Create new @reviq/common package with environment-agnostic utilities:
- Date formatting: formatDate, formatDateTime, formatLongDate,
  formatRelativeDate, formatRelativeTime
- User utilities: getUserInitials, formatRole

Consolidate date formatting from publisher-dashboard into shared package.
All utilities include comprehensive test coverage with bun:test.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/common/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "extends": "@macalinao/tsconfig/tsconfig.base.json",
+  "compilerOptions": {
+    "types": ["bun"]
+  }
+}