fix: serve data/ from disk via nginx alias; return full athlete data from API

docs/deployment/vps.md

@@ -236,6 +236,8 @@ server {
     root /var/www/bincio;
     index index.html;
 
+    client_max_body_size 512M;  # bulk activity uploads
+
     # API → bincio serve
     location /api/ {
         proxy_pass http://127.0.0.1:4041;
@@ -244,6 +246,13 @@ server {
         proxy_read_timeout 120s;   # Strava sync can be slow
     }
 
+    # Data files served live from disk — bypasses the build/rsync cycle
+    # so uploads and merges are visible immediately without a site rebuild.
+    location /data/ {
+        alias /var/bincio/data/;
+        add_header Cache-Control "no-cache, must-revalidate";
+    }
+
     # Static files
     location / {
         try_files $uri $uri/ $uri.html =404;