feat: P7 FormField komponenta + migrace Vehicles

- FormField.jsx: wrapper pro label + input + error pattern (aria-invalid podpora)
- Vehicles.jsx: migrovano na FormField (demonstrace patternu)
- Postupna migrace dalsich formularovych stranek v budoucnu

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/admin/components/FormField.jsx

@@ -0,0 +1,23 @@
+/**
+ * Formularovy wrapper pro label + input + error.
+ * Nahrazuje opakovany pattern admin-form-group + has-error + admin-form-error.
+ *
+ * @param {string} label - Text labelu
+ * @param {string} [error] - Chybova zprava (zobrazi se pod inputem)
+ * @param {boolean} [required] - Zobrazi cervenu hvezdicku
+ * @param {string} [className] - Extra CSS trida na wrapperu
+ * @param {React.ReactNode} children - Input/select/textarea element
+ */
+export default function FormField({ label, error, required, className, children }) {
+  const groupClass = `admin-form-group${error ? ' has-error' : ''}${className ? ` ${className}` : ''}`
+
+  return (
+    <div className={groupClass}>
+      <label className={`admin-form-label${required ? ' required' : ''}`}>
+        {label}
+      </label>
+      {children}
+      {error && <span className="admin-form-error">{error}</span>}
+    </div>
+  )
+}

src/admin/pages/Vehicles.jsx

@@ -8,6 +8,7 @@ import useModalLock from '../hooks/useModalLock'
 
 import { formatKm } from '../utils/formatters'
 import apiFetch from '../utils/api'
+import FormField from '../components/FormField'
 const API_BASE = '/api/admin'
 
 export default function Vehicles() {
@@ -338,8 +339,7 @@ export default function Vehicles() {
               <div className="admin-modal-body">
                 <div className="admin-form">
                   <div className="admin-form-row">
-                    <div className={`admin-form-group${errors.spz ? ' has-error' : ''}`}>
-                      <label className="admin-form-label required">SPZ</label>
+                    <FormField label="SPZ" error={errors.spz} required>
                       <input
                         type="text"
                         value={form.spz}
@@ -349,12 +349,11 @@ export default function Vehicles() {
                         }}
                         className="admin-form-input"
                         placeholder="1AB 2345"
+                        aria-invalid={!!errors.spz}
                       />
-                      {errors.spz && <span className="admin-form-error">{errors.spz}</span>}
-                    </div>
+                    </FormField>
 
-                    <div className={`admin-form-group${errors.name ? ' has-error' : ''}`}>
-                      <label className="admin-form-label required">Název</label>
+                    <FormField label="Název" error={errors.name} required>
                       <input
                         type="text"
                         value={form.name}
@@ -364,14 +363,13 @@ export default function Vehicles() {
                         }}
                         className="admin-form-input"
                         placeholder="Služební #1"
+                        aria-invalid={!!errors.name}
                       />
-                      {errors.name && <span className="admin-form-error">{errors.name}</span>}
-                    </div>
+                    </FormField>
                   </div>
 
                   <div className="admin-form-row">
-                    <div className="admin-form-group">
-                      <label className="admin-form-label">Značka</label>
+                    <FormField label="Značka">
                       <input
                         type="text"
                         value={form.brand}
@@ -379,10 +377,9 @@ export default function Vehicles() {
                         className="admin-form-input"
                         placeholder="Škoda"
                       />
-                    </div>
+                    </FormField>
 
-                    <div className="admin-form-group">
-                      <label className="admin-form-label">Model</label>
+                    <FormField label="Model">
                       <input
                         type="text"
                         value={form.model}
@@ -390,7 +387,7 @@ export default function Vehicles() {
                         className="admin-form-input"
                         placeholder="Octavia Combi"
                       />
-                    </div>
+                    </FormField>
                   </div>
 
                   <div className="admin-form-group">