debug: Add comprehensive console logging for workflow editor debugging

Debug Logs Added:
- useEffect: Log ID validation and loadWorkflow calls
- loadWorkflow: Log API response, graph_data, deserialization results
- handleNodeUpdate: Log updates and resulting node state
- handleSave: Log serialization, API calls, navigation

Bug Fixes:
- useEffect: Add !isNaN(parseInt(id)) check to prevent /api/prompts/NaN calls
- Prompt selection: String conversion for value prop (Number vs String mismatch)
  - <select value={String(selectedNode.data.prompt_id)}>
  - <option value={String(prompt.id)}>
  - onChange: find with String(p.id) === promptId

Issues to Debug:
- Why does useEffect run with id=undefined after navigate?
- Why does loadWorkflow not populate nodes/edges?
- Why does prompt selection not persist?

Next Step: User tests with Browser Console open, reports logs

frontend/src/pages/WorkflowEditorPage.jsx

@@ -62,8 +62,11 @@ export default function WorkflowEditorPage() {
 
   // Load workflow wenn ID vorhanden
   useEffect(() => {
-    if (id && id !== 'new') {
+    if (id && id !== 'new' && !isNaN(parseInt(id))) {
+      console.log('🔍 useEffect: Loading workflow with ID:', id)
       loadWorkflow(parseInt(id))
+    } else if (id && id !== 'new') {
+      console.error('❌ useEffect: Invalid ID (NaN):', id)
     }
   }, [id])
 
@@ -99,9 +102,12 @@ export default function WorkflowEditorPage() {
   }
 
   const handleNodeUpdate = (nodeId, updates) => {
-    setNodes((nds) =>
-      nds.map((n) => (n.id === nodeId ? { ...n, data: { ...n.data, ...updates } } : n))
-    )
+    console.log('🔧 handleNodeUpdate:', { nodeId, updates })
+    setNodes((nds) => {
+      const updated = nds.map((n) => (n.id === nodeId ? { ...n, data: { ...n.data, ...updates } } : n))
+      console.log('📝 Nodes after update:', updated.find(n => n.id === nodeId))
+      return updated
+    })
   }
 
   const handleDeleteNode = () => {
@@ -113,6 +119,7 @@ export default function WorkflowEditorPage() {
   }
 
   const handleSave = async () => {
+    console.log('💾 handleSave called')
     try {
       setLoading(true)
       setError(null)
@@ -129,9 +136,11 @@ export default function WorkflowEditorPage() {
         created_at: currentPrompt?.created_at,
         version: '1.0'
       })
+      console.log('📊 Serialized graph_data:', graph_data)
 
       if (currentPrompt) {
         // Update existing
+        console.log('📝 Updating existing workflow:', currentPrompt.id)
         await api.updateUnifiedPrompt(currentPrompt.id, {
           type: 'workflow',
           name: workflowName,
@@ -141,17 +150,21 @@ export default function WorkflowEditorPage() {
         alert('Workflow gespeichert!')
       } else {
         // Create new
+        console.log('✨ Creating new workflow')
         const result = await api.createUnifiedPrompt({
           type: 'workflow',
           name: workflowName,
           description: workflowDescription,
           graph_data
         })
+        console.log('✅ Workflow created:', result)
         setCurrentPrompt({ id: result.id, name: workflowName })
         alert('Workflow erstellt!')
+        console.log('🚀 Navigating to:', `/workflow-editor/${result.id}`)
         navigate(`/workflow-editor/${result.id}`)
       }
     } catch (e) {
+      console.error('❌ handleSave error:', e)
       setError(e.message)
     } finally {
       setLoading(false)
@@ -159,11 +172,14 @@ export default function WorkflowEditorPage() {
   }
 
   const loadWorkflow = async (promptId) => {
+    console.log('📦 loadWorkflow called with:', promptId)
     try {
       setLoading(true)
       setError(null)
 
       const prompt = await api.getPrompt(promptId)
+      console.log('✅ Prompt loaded:', prompt)
+      console.log('📊 graph_data:', prompt.graph_data)
 
       if (prompt.type !== 'workflow') {
         throw new Error('Nicht ein Workflow')
@@ -171,6 +187,7 @@ export default function WorkflowEditorPage() {
 
       // Deserialisieren
       const { nodes: loadedNodes, edges: loadedEdges } = deserializeFromWorkflowGraph(prompt.graph_data)
+      console.log('🎯 Deserialized:', { nodes: loadedNodes, edges: loadedEdges })
 
       setNodes(loadedNodes)
       setEdges(loadedEdges)
@@ -184,7 +201,9 @@ export default function WorkflowEditorPage() {
         0
       )
       nodeIdCounter = maxId + 1
+      console.log('✅ Workflow loaded successfully, nodes:', loadedNodes.length, 'edges:', loadedEdges.length)
     } catch (e) {
+      console.error('❌ loadWorkflow error:', e)
       setError(e.message)
     } finally {
       setLoading(false)
@@ -393,10 +412,12 @@ export default function WorkflowEditorPage() {
                 <div className="config-section">
                   <label>KI-Prompt auswählen</label>
                   <select
-                    value={selectedNode.data.prompt_id || ''}
+                    value={selectedNode.data.prompt_id ? String(selectedNode.data.prompt_id) : ''}
                     onChange={(e) => {
                       const promptId = e.target.value
-                      const selectedPrompt = availablePrompts.find(p => p.id === parseInt(promptId))
+                      console.log('🎯 Prompt selected:', promptId, 'Type:', typeof promptId)
+                      const selectedPrompt = availablePrompts.find(p => String(p.id) === promptId)
+                      console.log('📋 Selected prompt object:', selectedPrompt)
                       handleNodeUpdate(selectedNode.id, {
                         prompt_id: promptId ? parseInt(promptId) : null,
                         prompt_name: selectedPrompt?.name || null
@@ -413,14 +434,14 @@ export default function WorkflowEditorPage() {
                   >
                     <option value="">-- Basis-Prompt wählen --</option>
                     {availablePrompts.map(prompt => (
-                      <option key={prompt.id} value={prompt.id}>
+                      <option key={prompt.id} value={String(prompt.id)}>
                         {prompt.name}
                       </option>
                     ))}
                   </select>
-                  {selectedNode.data.prompt_name && (
+                  {selectedNode.data.prompt_id && (
                     <div style={{ marginTop: 8, fontSize: 12, color: 'var(--text3)' }}>
-                      Gewählt: {selectedNode.data.prompt_name}
+                      Prompt ID: {selectedNode.data.prompt_id} ({selectedNode.data.prompt_name || 'unbekannt'})
                     </div>
                   )}
                 </div>