fix: use WEB_CONCURRENCY env var for gunicorn workers

Replace hardcoded `-w 2` with `${WEB_CONCURRENCY:-1}` to allow
runtime control. Default to 1 worker to avoid SQLite concurrent
access race during lifespan startup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pythoninthegrass

app/startup.sh

@@ -12,7 +12,7 @@ export PATH="${VENV}/bin:$HOME/.asdf/bin:$HOME/.asdf/shims:$PATH"
 
 server() {
 	gunicorn \
-		-w 2 \
+		-w "${WEB_CONCURRENCY:-1}" \
 		-k uvicorn.workers.UvicornWorker main:app \
 		-b "0.0.0.0:${PORT:-3000}" \
 		--log-file -