fix: add dsh-web restart-persistent authentication

- Add capture-dsh-token.sh script that captures the dsh-web launch token
- Add login endpoint (/dsh-web-login on :8081) that mints 30-day auth cookie
- Document the authentication flow in zulip-health.prose.md (Platform B4)
- Cookie is authority-bound to 127.0.0.1:3080 with 30-day expiry
- After first login, subsequent requests use the cookie — no token required

scripts/capture-dsh-token.sh

@@ -0,0 +1,77 @@
+#!/bin/bash
+# capture-dsh-token.sh — start dsh-web, capture its token, update nginx
+# Run on CT112 (tankodhs.sysloggh.net)
+# This script:
+# 1. Restarts the dsh-web service
+# 2. Captures the token URL from the journal
+# 3. Extracts the token value
+# 4. Writes the token to /etc/dsh-web/launch-token
+# 5. Creates an nginx config that exposes a /dsh-web-login endpoint
+# 6. Reloads nginx
+
+set -euo pipefail
+
+# Kill any existing dsh-web instance first
+systemctl stop dsh-web 2>/dev/null || true
+sleep 2
+
+# Record the time we started the service (for --since filter)
+START_TIME="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+
+# Start dsh-web
+systemctl start dsh-web
+
+# Wait for the token to appear in the journal (up to 30 seconds)
+TOKEN=""
+for i in {1..30}; do
+  TOKEN=$(journalctl -u dsh-web.service --since "$START_TIME" --output=cat 2>/dev/null | grep -m1 "dsh web: http://" | grep -oP "(?<=dsh web: )(https?://[^ ]+)" | head -1 || true)
+  if [ -n "$TOKEN" ]; then
+    break
+  fi
+  sleep 1
+done
+
+if [ -z "$TOKEN" ]; then
+  echo "ERROR: token not captured within 30s" >&2
+  exit 1
+fi
+
+# Extract the token value (everything after "?token=")
+TOKEN_VALUE=$(echo "$TOKEN" | grep -oP "(?<=token=)[^ ]+")
+
+# Write the token to a file
+mkdir -p /etc/dsh-web
+echo "$TOKEN_VALUE" > /etc/dsh-web/launch-token
+echo "Captured token: $TOKEN_VALUE"
+
+# Create the nginx config with the token (using printf to control expansion)
+{
+  printf "server {\n"
+  printf "    listen 8081;\n"
+  printf "    server_name _;\n"
+  printf "    \n"
+  printf "    location /dsh-web-login {\n"
+  printf "        proxy_pass http://127.0.0.1:3080/?token=%s;\n" "$TOKEN_VALUE"
+  printf "        proxy_http_version 1.1;\n"
+  printf "        proxy_set_header Host 127.0.0.1:3080;\n"
+  printf "        proxy_set_header X-Real-IP \$remote_addr;\n"
+  printf "        proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;\n"
+  printf "    }\n"
+  printf "    \n"
+  printf "    location / {\n"
+  printf "        proxy_pass http://127.0.0.1:3080;\n"
+  printf "        proxy_http_version 1.1;\n"
+  printf "        proxy_set_header Host 127.0.0.1:3080;\n"
+  printf "        proxy_set_header X-Real-IP \$remote_addr;\n"
+  printf "        proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;\n"
+  printf "    }\n"
+  printf "}\n"
+} > /etc/nginx/sites-enabled/dsh.token
+
+# Reload nginx
+nginx -t && /usr/sbin/nginx -s reload || {
+  echo "ERROR: failed to reload nginx" >&2
+  exit 1
+}
+
+echo "Token captured and nginx reloaded"