Fix start.sh: redirect uvicorn output to Docker logs

uvicorn was running in background with no output capture,
making it impossible to debug crashes. Now redirects stderr
to stdout and checks if uvicorn started successfully.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

start.sh

@@ -1,13 +1,20 @@
 #!/bin/sh
 # Start FastAPI backend + Next.js frontend in the same container.
-# Uvicorn runs in the background; Node.js runs in the foreground
-# so that Docker gets its exit signal from the primary process.
+# Both processes log to stdout/stderr so Docker captures everything.
 
 set -e
 
-echo "Starting FastAPI backend on :8000 ..."
-uvicorn web.app:app --host 127.0.0.1 --port 8000 --workers 1 &
+echo "[start.sh] Starting FastAPI backend on :8000 ..."
+uvicorn web.app:app --host 127.0.0.1 --port 8000 --workers 1 2>&1 &
 UVICORN_PID=$!
 
-echo "Starting Next.js frontend on :3000 ..."
-exec node server.js
+# Give uvicorn a moment to start (or crash)
+sleep 2
+
+if ! kill -0 $UVICORN_PID 2>/dev/null; then
+  echo "[start.sh] ERROR: uvicorn failed to start!"
+  # Don't exit — let Node.js run so the UI is accessible for debugging
+fi
+
+echo "[start.sh] Starting Next.js frontend on :3000 ..."
+node server.js