Use nginx restart instead of reload for blue-green switch (#5260)

nginx reload doesn't always force DNS re-resolution in Docker. During
blue-green deployment, after updating nginx.conf to point to the new
instance (e.g., eagle-green:40032), nginx -s reload would sometimes
keep trying to connect to the old (now removed) container, causing
502 errors.

A full restart ensures nginx picks up the new upstream correctly.
The ~1-2 second restart time is acceptable for deployment reliability.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

scripts/deploy-blue-green.sh

@@ -221,7 +221,7 @@ main() {
         echo "JFR_SIDECAR_ADDR=jfr-sidecar:8081" >> "${env_file}"
     fi
 
-    # Validate nginx config before reload
+    # Validate nginx config before restart
     log_info "Validating nginx configuration..."
     if ! docker exec nginx nginx -t 2>&1; then
         log_error "nginx config validation failed, aborting!"
@@ -230,12 +230,12 @@ main() {
         exit 1
     fi
 
-    # Reload nginx (use reload for faster switch, restart if reload fails)
-    log_info "Reloading nginx..."
-    if ! docker exec nginx nginx -s reload 2>/dev/null; then
-        log_warn "Reload failed, restarting nginx..."
-        docker compose -f "${COMPOSE_FILE}" restart nginx
-    fi
+    # Restart nginx to pick up new upstream
+    # Note: We use restart instead of reload because reload doesn't always
+    # force DNS re-resolution in Docker, causing nginx to keep trying to
+    # connect to the old (removed) container
+    log_info "Restarting nginx..."
+    docker compose -f "${COMPOSE_FILE}" restart nginx
 
     # Restart admin to pick up new .env
     log_info "Restarting admin service..."