docs: add API documentation for frontend integration and include response timing metrics

ai-patient-onboarding/app/api/voice_onboarding.py

@@ -350,6 +350,7 @@ async def complete_voice_onboarding(
     request: CompleteOnboardingRequest,
     db: Session = Depends(get_db),
 ):
+    start_time = time.time()
     onboarding_service = OnboardingService()
     completion_service = CompletionService()
     result_service = ResultExtractionService()
@@ -384,6 +385,10 @@ async def complete_voice_onboarding(
         conversation_history=conversation_history,
     )
 
+    elapsed = time.time() - start_time
+    resp_ms = round(elapsed * 1000, 2)
+    resp_sec = round(elapsed, 3)
+
     if not request.confirmed:
         return CompleteOnboardingResponse(
             success=True,
@@ -391,6 +396,8 @@ async def complete_voice_onboarding(
             status="awaiting_confirmation",
             result=result,
             message="Please review the collected information and confirm by voice or tap.",
+            response_time_ms=resp_ms,
+            response_time_sec=resp_sec,
         )
 
     submission = await submission_service.submit(result)
@@ -407,6 +414,8 @@ async def complete_voice_onboarding(
             status="submitted_and_cleaned",
             result=result,
             message="Voice onboarding successfully saved to patient record.",
+            response_time_ms=resp_ms,
+            response_time_sec=resp_sec,
         )
 
     session.status = "submission_pending_retry"
@@ -418,4 +427,6 @@ async def complete_voice_onboarding(
         status="submission_pending_retry",
         result=result,
         message="Patient API submission failed. Session preserved for retry.",
+        response_time_ms=resp_ms,
+        response_time_sec=resp_sec,
     )