Frontend: locks vom Backend, uiError sichtbar, Pausiert-Badge, Inline-Progress, Mobile-Exklusivität, Fehler-Persistenz

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/api.js

@@ -1,17 +1,35 @@
 const BASE = '/api'
 
+// Backend-Fehler (400/409 mit detail) als Error werfen statt sie zu verschlucken
+async function jsonOrThrow(res) {
+  if (!res.ok) {
+    let detail = `Fehler (HTTP ${res.status})`
+    try {
+      const data = await res.json()
+      if (data.detail) detail = typeof data.detail === 'string' ? data.detail : JSON.stringify(data.detail)
+    } catch { /* kein JSON-Body */ }
+    throw new Error(detail)
+  }
+  return res.json()
+}
+
 export async function fetchGuides() {
   const res = await fetch(`${BASE}/guides`)
   return res.json()
 }
 
+export async function fetchGuideLocks(topic) {
+  const res = await fetch(`${BASE}/guides/locks?topic=${encodeURIComponent(topic)}`)
+  return res.json()
+}
+
 export async function createGuide(topic, format, instructions = '', provider = 'claude') {
   const res = await fetch(`${BASE}/guides`, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ topic, format, instructions, provider }),
   })
-  return res.json()
+  return jsonOrThrow(res)
 }
 
 export async function fetchActiveBausteine() {
@@ -30,7 +48,7 @@ export async function createBausteine(topic, instructions = '', provider = 'clau
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ topic, instructions, provider }),
   })
-  return res.json()
+  return jsonOrThrow(res)
 }
 
 export async function cancelBausteine(topic) {