fix: Use SSE streaming in WorkflowExecutePanel to prevent 504 timeout

ROOT CAUSE:
- WorkflowExecutePanel used api.executeWorkflow (synchronous POST)
- Long workflows (10+ nodes, 60-90s) → 504 Gateway Timeout
- Reverse proxy kills request after 60s

SOLUTION:
- Switch to api.executeUnifiedPromptStream (SSE)
- Real-time progress updates during execution
- No timeout (streaming connection stays alive)
- Progress display: X/Y Nodes • Current node label

Changes:
- Replace executeWorkflow with executeUnifiedPromptStream
- Add progress callback for node_complete events
- Add progress state + UI display
- Flexbox column layout for progress bar

Fixes: 504 Gateway Timeout bei langen Workflows im Workflow Designer

frontend/src/components/workflow/panels/WorkflowExecutePanel.jsx

@@ -6,11 +6,10 @@ import { api } from '../../../utils/api'
  *
  * Features:
  * - Execute Button mit Loading State
+ * - SSE Streaming (kein Timeout bei langen Workflows)
+ * - Real-time Progress
  * - Error Handling
- * - Success State
  * - Debug Mode Toggle
- *
- * Part 2: Frontend Execute Integration
  */
 export function WorkflowExecutePanel({
   currentPrompt,
@@ -20,6 +19,7 @@ export function WorkflowExecutePanel({
   const [executing, setExecuting] = useState(false)
   const [error, setError] = useState(null)
   const [debugMode, setDebugMode] = useState(true)
+  const [progress, setProgress] = useState(null)
 
   const handleExecute = async () => {
     if (!currentPrompt || !currentPrompt.slug) {
@@ -30,14 +30,28 @@ export function WorkflowExecutePanel({
     try {
       setExecuting(true)
       setError(null)
+      setProgress({ current: 0, total: 0, label: 'Starte...' })
 
-      console.log('🚀 Executing workflow:', currentPrompt.slug)
+      console.log('🚀 Executing workflow via SSE:', currentPrompt.slug)
 
-      const result = await api.executeWorkflow(
+      const result = await api.executeUnifiedPromptStream(
         currentPrompt.slug,
-        null,  // variables (später erweiterbar)
+        null,  // modules
+        null,  // timeframes
         debugMode,
-        false  // save (nicht in ai_insights speichern)
+        false,  // save (nicht in ai_insights speichern)
+        (event) => {
+          // Progress callback für real-time updates
+          if (event.type === 'execution_started') {
+            setProgress({ current: 0, total: 0, label: 'Gestartet...' })
+          } else if (event.type === 'node_complete') {
+            setProgress({
+              current: event.completed_nodes || 0,
+              total: event.total_nodes || 0,
+              label: event.node_label || 'Processing...'
+            })
+          }
+        }
       )
 
       console.log('✅ Workflow execution completed:', result)
@@ -57,81 +71,107 @@ export function WorkflowExecutePanel({
       setError(e.message)
     } finally {
       setExecuting(false)
+      setProgress(null)
     }
   }
 
   return (
-    <div style={{ display: 'flex', gap: '8px', alignItems: 'center' }}>
+    <div style={{ display: 'flex', flexDirection: 'column', gap: '8px' }}>
-      {/* Debug Mode Toggle */}
+      <div style={{ display: 'flex', gap: '8px', alignItems: 'center' }}>
-      <label
+        {/* Debug Mode Toggle */}
-        style={{
+        <label
-          display: 'flex',
+          style={{
-          alignItems: 'center',
+            display: 'flex',
-          gap: '4px',
+            alignItems: 'center',
+            gap: '4px',
+            fontSize: '12px',
+            color: 'var(--text2)',
+            cursor: 'pointer'
+          }}
+          title="Debug-Modus zeigt detaillierte Node-States im Ergebnis"
+        >
+          <input
+            type="checkbox"
+            checked={debugMode}
+            onChange={(e) => setDebugMode(e.target.checked)}
+            disabled={executing}
+          />
+          Debug
+        </label>
+
+        {/* Execute Button */}
+        <button
+          className="btn-primary"
+          onClick={handleExecute}
+          disabled={disabled || executing || !currentPrompt}
+          title={
+            !currentPrompt
+              ? 'Workflow muss zuerst gespeichert werden'
+              : disabled
+              ? 'Workflow hat Validierungsfehler'
+              : 'Workflow ausführen'
+          }
+          style={{
+            minWidth: '120px',
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'center',
+            gap: '8px'
+          }}
+        >
+          {executing ? (
+            <>
+              <span className="spinner" style={{ width: 14, height: 14 }} />
+              Executing...
+            </>
+          ) : (
+            <>
+              ▶️ Execute
+            </>
+          )}
+        </button>
+
+        {/* Error Display */}
+        {error && (
+          <div
+            style={{
+              padding: '6px 12px',
+              background: 'var(--danger)',
+              color: 'white',
+              borderRadius: '4px',
+              fontSize: '12px',
+              maxWidth: '300px',
+              overflow: 'hidden',
+              textOverflow: 'ellipsis',
+              whiteSpace: 'nowrap'
+            }}
+            title={error}
+          >
+            ❌ {error}
+          </div>
+        )}
+      </div>
+
+      {/* Progress Display */}
+      {progress && (
+        <div style={{
+          padding: '8px 12px',
+          background: 'var(--surface2)',
+          borderRadius: '4px',
           fontSize: '12px',
           color: 'var(--text2)',
-          cursor: 'pointer'
-        }}
-        title="Debug-Modus zeigt detaillierte Node-States im Ergebnis"
-      >
-        <input
-          type="checkbox"
-          checked={debugMode}
-          onChange={(e) => setDebugMode(e.target.checked)}
-          disabled={executing}
-        />
-        Debug
-      </label>
-
-      {/* Execute Button */}
-      <button
-        className="btn-primary"
-        onClick={handleExecute}
-        disabled={disabled || executing || !currentPrompt}
-        title={
-          !currentPrompt
-            ? 'Workflow muss zuerst gespeichert werden'
-            : disabled
-            ? 'Workflow hat Validierungsfehler'
-            : 'Workflow ausführen'
-        }
-        style={{
-          minWidth: '120px',
           display: 'flex',
           alignItems: 'center',
-          justifyContent: 'center',
           gap: '8px'
-        }}
+        }}>
-      >
+          <span className="spinner" style={{ width: 12, height: 12 }} />
-        {executing ? (
+          <span>
-          <>
+            {progress.total > 0
-            <span className="spinner" style={{ width: 14, height: 14 }} />
+              ? `${progress.current}/${progress.total} Nodes`
-            Executing...
+              : 'Läuft...'
-          </>
+            }
-        ) : (
+            {progress.label && ` • ${progress.label}`}
-          <>
+          </span>
-            ▶️ Execute
-          </>
-        )}
-      </button>
-
-      {/* Error Display */}
-      {error && (
-        <div
-          style={{
-            padding: '6px 12px',
-            background: 'var(--danger)',
-            color: 'white',
-            borderRadius: '4px',
-            fontSize: '12px',
-            maxWidth: '300px',
-            overflow: 'hidden',
-            textOverflow: 'ellipsis',
-            whiteSpace: 'nowrap'
-          }}
-          title={error}
-        >
-          ❌ {error}
         </div>
       )}
     </div>