fix: Add wrapper in prompts.py execute endpoint for workflow signature mismatch

Problem: Workflows executed via /api/prompts/execute (not /api/workflows/execute)
were passing call_openrouter directly to execute_prompt_with_data, which then
passes it to workflow_executor. workflow_executor expects (prompt, model) signature
but call_openrouter has (prompt, max_tokens=4096) signature.

Previous fix in workflows.py was correct but unused - workflows use prompts.py endpoint.

Solution: Added workflow_llm_call() wrapper in execute_unified_prompt() endpoint
that matches expected (prompt, model) -> str signature.

Related: cb3aa48 (workflows.py fix for different endpoint)

backend/routers/prompts.py

@@ -1488,6 +1488,14 @@ async def execute_unified_prompt(
             'vitalwerte': 7
         }
 
+    # Wrapper function to match workflow_executor's expected signature: (prompt, model) -> str
+    # workflow_executor calls: openrouter_call_func(prompt, "anthropic/claude-sonnet-4")
+    # but call_openrouter expects: call_openrouter(prompt, max_tokens=4096)
+    async def workflow_llm_call(prompt: str, model: str = None) -> str:
+        # Ignore model parameter (already set in OPENROUTER_MODEL env var)
+        # Use default max_tokens=4096 from call_openrouter
+        return await call_openrouter(prompt)
+
     # Execute with prompt_executor
     # Always enable debug when saving to collect metadata for value table
     result = await execute_prompt_with_data(
@@ -1495,7 +1503,7 @@ async def execute_unified_prompt(
         profile_id=profile_id,
         modules=modules,
         timeframes=timeframes,
-        openrouter_call_func=call_openrouter,
+        openrouter_call_func=workflow_llm_call,  # Use wrapper with correct signature
         enable_debug=debug or save  # Enable debug if saving for metadata collection
     )