fix(reactive-resume): fix PDF generation timeout in LXC containers (#14278)

Two changes to resolve Puppeteer waitForFunction timeout (5000ms exceeded):

1. Use 127.0.0.1 instead of localhost for PRINTER_ENDPOINT to avoid
   potential IPv6 resolution issues in LXC containers where 'localhost'
   may resolve to ::1 while Chromium only listens on 127.0.0.1.

2. Add --no-zygote flag to the chromium-printer service. In LXC
   containers the Zygote process (used by Chrome for process forking)
   can fail silently, causing Puppeteer page rendering to hang until
   the printer timeout is exceeded.

install/reactive-resume-install.sh

@@ -55,7 +55,7 @@ DATABASE_URL=postgresql://${PG_DB_USER}:${PG_DB_PASS}@localhost:5432/${PG_DB_NAM
 AUTH_SECRET=${AUTH_SECRET}
 
 # Printer (headless Chromium for PDF generation)
-PRINTER_ENDPOINT=http://localhost:9222
+PRINTER_ENDPOINT=http://127.0.0.1:9222
 
 # Storage: uses local filesystem (/opt/reactive-resume/data) when S3 is not configured
 # S3_ACCESS_KEY_ID=
@@ -92,7 +92,7 @@ After=network.target
 
 [Service]
 Type=simple
-ExecStart=/usr/bin/chromium --headless --disable-gpu --no-sandbox --disable-dev-shm-usage --remote-debugging-address=127.0.0.1 --remote-debugging-port=9222
+ExecStart=/usr/bin/chromium --headless --disable-gpu --no-sandbox --no-zygote --disable-dev-shm-usage --remote-debugging-address=127.0.0.1 --remote-debugging-port=9222
 Restart=always
 RestartSec=5