feat(design-system): add reusable FormField wrapper primitive

Standalone, OnPush. Label/hint/error slots, required marker, aria-describedby
wiring, role=alert on error. Colors via existing tenant CSS vars with fallbacks.

src/app/shared/ui/form-field/form-field.component.html

@@ -0,0 +1,23 @@
+<div class="app-form-field">
+  @if (label()) {
+    <label class="app-form-field__label" [for]="fieldId">
+      {{ label() }}
+      @if (required()) {
+        <span class="app-form-field__required" aria-hidden="true">*</span>
+      }
+    </label>
+  }
+
+  <div
+    class="app-form-field__control"
+    [attr.aria-describedby]="error() ? errorId : (hint() ? hintId : null)"
+  >
+    <ng-content />
+  </div>
+
+  @if (error()) {
+    <p class="app-form-field__error" [id]="errorId" role="alert">{{ error() }}</p>
+  } @else if (hint()) {
+    <p class="app-form-field__hint" [id]="hintId">{{ hint() }}</p>
+  }
+</div>

src/app/shared/ui/form-field/form-field.component.scss

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+.app-form-field {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-xs, 0.25rem);
+}
+
+.app-form-field__label {
+  font-size: 0.875rem;
+  font-weight: 600;
+  color: var(--text-primary, #1f322d);
+}
+
+.app-form-field__required {
+  color: var(--error-color, #c0392b);
+  margin-left: 0.125rem;
+}
+
+.app-form-field__control {
+  display: block;
+}
+
+.app-form-field__hint {
+  margin: 0;
+  font-size: 0.8125rem;
+  color: var(--text-secondary, #6b7280);
+}
+
+.app-form-field__error {
+  margin: 0;
+  font-size: 0.8125rem;
+  color: var(--error-color, #c0392b);
+}

src/app/shared/ui/form-field/form-field.component.ts

@@ -0,0 +1,21 @@
+import { ChangeDetectionStrategy, Component, input } from '@angular/core';
+
+let nextFormFieldId = 0;
+
+@Component({
+  selector: 'app-form-field',
+  standalone: true,
+  templateUrl: './form-field.component.html',
+  styleUrl: './form-field.component.scss',
+  changeDetection: ChangeDetectionStrategy.OnPush
+})
+export class FormFieldComponent {
+  readonly label = input<string | null>(null);
+  readonly hint = input<string | null>(null);
+  readonly error = input<string | null>(null);
+  readonly required = input(false);
+
+  protected readonly fieldId = `app-form-field-${++nextFormFieldId}`;
+  protected readonly hintId = `${this.fieldId}-hint`;
+  protected readonly errorId = `${this.fieldId}-error`;
+}