feat(design-system): add reusable EmptyState primitive

Standalone, OnPush. title required input (caller supplies translated text),
optional description, icon/actions content-projection slots. Colors via
existing tenant CSS vars with fallbacks.

src/app/shared/ui/empty-state/empty-state.component.html

@@ -0,0 +1,12 @@
+<div class="app-empty-state">
+  <div class="app-empty-state__icon">
+    <ng-content select="[slot=icon]" />
+  </div>
+  <h3 class="app-empty-state__title">{{ title() }}</h3>
+  @if (description()) {
+    <p class="app-empty-state__description">{{ description() }}</p>
+  }
+  <div class="app-empty-state__actions">
+    <ng-content select="[slot=actions]" />
+  </div>
+</div>

src/app/shared/ui/empty-state/empty-state.component.scss

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+.app-empty-state {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  text-align: center;
+  gap: var(--space-sm, 0.5rem);
+  padding: var(--space-xl, 2rem) var(--space-lg, 1.5rem);
+  color: var(--text-secondary, #6b7280);
+}
+
+.app-empty-state__icon {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  color: var(--text-secondary, #6b7280);
+
+  &:empty {
+    display: none;
+  }
+}
+
+.app-empty-state__title {
+  margin: 0;
+  font-size: 1.0625rem;
+  font-weight: 600;
+  color: var(--text-primary, #1f322d);
+}
+
+.app-empty-state__description {
+  margin: 0;
+  max-width: 32rem;
+  font-size: 0.875rem;
+}
+
+.app-empty-state__actions {
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm, 0.5rem);
+  margin-top: var(--space-xs, 0.25rem);
+
+  &:empty {
+    display: none;
+  }
+}

src/app/shared/ui/empty-state/empty-state.component.ts

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+import { ChangeDetectionStrategy, Component, input } from '@angular/core';
+
+@Component({
+  selector: 'app-empty-state',
+  standalone: true,
+  templateUrl: './empty-state.component.html',
+  styleUrl: './empty-state.component.scss',
+  changeDetection: ChangeDetectionStrategy.OnPush
+})
+export class EmptyStateComponent {
+  readonly title = input.required<string>();
+  readonly description = input<string | null>(null);
+}