Add create modal for words and pictures tables

- + Button in TableView for tables with a create form (words, pictures)
- Words: form with titel_de/en/sv + difficulty_level → POST /words
- Pictures: design field + image uploader → POST /pictures then POST /pictures/:id/upload
- Image drag-drop area with preview before upload, sends multipart to Hetzner via API
- New record prepended to table on success
- apiPost + apiUpload helpers added to api.js

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

src/lib/api.js

@@ -62,6 +62,29 @@ export async function apiPatch(endpoint, id, body) {
   });
 }
 
+export async function apiPost(endpoint, body) {
+  return apiFetch(endpoint, {
+    method: 'POST',
+    body: JSON.stringify(body),
+  });
+}
+
 export async function apiFetchOne(path) {
   return apiFetch(path);
 }
+
+// Multipart upload — does NOT set Content-Type (browser sets boundary automatically)
+export async function apiUpload(path, formData) {
+  const token = getToken();
+  const res = await fetch(`${API_URL}${path}`, {
+    method: 'POST',
+    headers: token ? { Authorization: `Bearer ${token}` } : {},
+    body: formData,
+  });
+  if (res.status === 401) { logout(); window.location.href = '/login'; return; }
+  if (!res.ok) {
+    const err = await res.json().catch(() => ({}));
+    throw new Error(err.error || `HTTP ${res.status}`);
+  }
+  return res.json();
+}