feat: registration field polish, multi-category tags, file uploads, Partner icon

- Restructure field editor dialog: move Options section to bottom with
  divider and subheader, fix delete button with flex layout
- Change tag_category (single string) to tag_categories (JSON array)
  supporting multiple category selection in tag picker fields
- Portal tag picker now groups tags by category with subheaders
- Add generic file upload endpoint (FileUploadService + UploadController)
- Replace email branding logo URL text field with ImageUploadField
- Update Partner crowd type default icon to tabler-affiliate
- Apply changes consistently to both field and template dialogs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/portal/src/pages/register/[eventSlug].vue

@@ -263,6 +263,21 @@ function isMultiValueType(t: RegistrationFieldType): boolean {
   return t === 'multiselect' || t === 'checkbox' || t === 'tag_picker'
 }
 
+function groupedTagItems(tags: Array<{ id: string; name: string; category: string | null }>) {
+  const items: Array<{ type?: string; title: string; value?: string }> = []
+  let lastCategory: string | null = null
+
+  for (const tag of tags) {
+    if (tag.category !== lastCategory) {
+      items.push({ type: 'subheader', title: tag.category ?? 'Overig' })
+      lastCategory = tag.category
+    }
+    items.push({ title: tag.name, value: tag.id })
+  }
+
+  return items
+}
+
 function isEmptyFieldValue(value: unknown, type: RegistrationFieldType): boolean {
   if (value === undefined || value === null) return true
   if (value === '') return true
@@ -1251,7 +1266,7 @@ async function onSubmit() {
                           :error-messages="fieldErrors[field.slug]"
                         />
 
-                        <VSelect
+                        <VAutocomplete
                           v-else-if="field.field_type === 'tag_picker'"
                           v-model="fieldFormData[field.slug] as string[]"
                           variant="outlined"
@@ -1260,9 +1275,9 @@ async function onSubmit() {
                           multiple
                           chips
                           closable-chips
-                          :items="field.available_tags ?? []"
-                          item-title="name"
-                          item-value="id"
+                          :items="groupedTagItems(field.available_tags ?? [])"
+                          item-title="title"
+                          item-value="value"
                           :label="field.label + (field.is_required ? ' *' : '')"
                           :hint="field.help_text ?? undefined"
                           persistent-hint

apps/portal/src/types/registration.ts

@@ -30,7 +30,7 @@ export interface RegistrationField {
   field_type: RegistrationFieldType
   options: (string | { label: string; description?: string | null })[] | null
   normalized_options: NormalizedOption[] | null
-  tag_category: string | null
+  tag_categories: string[] | null
   is_required: boolean
   help_text: string | null
   display_width: FieldDisplayWidth