docs: update documentation for v0.4.0 release

- Update README.md with v0.4.0 features and screenshots placeholders
- Update architecture.md with v0.4.0 implementation status
- Update progress.md marking all 27 tasks as completed
- Create CHANGELOG.md with complete release notes
- Add v0.4.0 frontend components and hooks

frontend/src/components/ui/toast-utils.ts

@@ -0,0 +1,14 @@
+interface Toast {
+  id: string
+  title?: string
+  description?: string
+  variant?: 'default' | 'destructive'
+}
+
+// Toast helper function - exported separately to avoid fast refresh issues
+export function showToast(props: Omit<Toast, 'id'>) {
+  window.dispatchEvent(new CustomEvent('toast', { detail: props }))
+}
+
+// Re-export Toast type for consumers
+export type { Toast };