feat(api): add ephemeral storage warning to results (BUG-005)

- Add warning field to SegmentResponse schema
- Include warning message in job completion result:
"Results are temporary and will be lost if Space restarts"
- Update frontend types to include warning in Metrics
- Display yellow warning banner in MetricsPanel when present

frontend/src/components/MetricsPanel.tsx

@@ -40,6 +40,13 @@ export function MetricsPanel({ metrics }: MetricsPanelProps) {
           </span>
         </div>
       </div>
+
+      {/* Ephemeral storage warning */}
+      {metrics.warning && (
+        <div className="mt-3 p-2 bg-yellow-900/30 border border-yellow-600/50 rounded text-xs text-yellow-300">
+          {metrics.warning}
+        </div>
+      )}
     </div>
   )
 }

src/stroke_deepisles_demo/api/routes.py

@@ -244,6 +244,7 @@ def run_segmentation_job(
             "elapsedSeconds": round(result.elapsed_seconds, 2),
             "dwiUrl": f"{backend_url}{file_path_prefix}/{dwi_filename}",
             "predictionUrl": f"{backend_url}{file_path_prefix}/{pred_filename}",
+            "warning": "Results are temporary and will be lost if the Space restarts. Download promptly.",
         }
 
         # Mark as completed

src/stroke_deepisles_demo/api/schemas.py

@@ -27,6 +27,9 @@ class SegmentResponse(BaseModel):
     elapsedSeconds: float
     dwiUrl: str
     predictionUrl: str
+    warning: str | None = Field(
+        None, description="Warning message about result storage (e.g., ephemeral disk)"
+    )
 
 
 # Job status type for strong typing