Standardize paths, add version endpoint, request timeouts, HOST env var, graceful shutdown

Cross-platform hardening — removes all hardcoded /app/ paths from route files
and routes them through platform-paths.js so the app works the same way
regardless of Docker layout (single-file mount vs consolidated data dir).

Changes:
- platform-paths.js: add generatedCertsDir, pkiDir, containerUpdatesDir,
  containerFrontendDir, containerAssetsDir, resolveAssetsPath()
- self-updater.js: UPDATE_URL/MIRROR_URL/CHANNEL env var overrides
- routes/ca.js: use platformPaths for cert paths and generated certs dir
- routes/services.js: use platformPaths.pkiRootCert
- routes/themes.js: derive THEMES_DIR from platformPaths.servicesFile
- routes/config/assets.js + backup.js: use resolveAssetsPath() fallback
- routes/services.js + src/app.js: use platformPaths.pkiRootCert
- server.js: HOST env var support, parse PORT as int
- src/app.js: GET /api/v1/version (public, no auth), global request timeout,
  disable x-powered-by, trust proxy
- pylon/dashcaddy-pylon.js: PYLON_HOST env var, graceful shutdown on SIGTERM/SIGINT

A fresh user can now deploy with a custom Docker layout (e.g. /opt/dc/data/
as a single volume mount) and the app finds its files automatically, no env
var configuration required.

dashcaddy-api/src/app.js

@@ -16,6 +16,7 @@ const { asyncHandler } = require('./utils/async-handler');
 
 // Managers and utilities
 const StateManager = require('../state-manager');
+const platformPaths = require('../platform-paths');
 const { LicenseManager } = require('../license-manager');
 const credentialManager = require('../credential-manager');
 const authManager = require('../auth-manager');
@@ -96,6 +97,19 @@ const { APP } = require('../constants');
 async function createApp() {
   const app = express();
 
+  // Global request timeout (default 5 minutes — covers slow Docker pulls)
+  // Routes that need longer can override per-request with req.setTimeout()
+  const REQUEST_TIMEOUT_MS = parseInt(process.env.REQUEST_TIMEOUT_MS, 10) || 5 * 60 * 1000;
+  app.use((req, res, next) => {
+    req.setTimeout(REQUEST_TIMEOUT_MS);
+    res.setTimeout(REQUEST_TIMEOUT_MS);
+    next();
+  });
+  // Disable x-powered-by header for security (don't advertise framework)
+  app.disable('x-powered-by');
+  // Trust first proxy (Caddy/nginx in front of us) so req.ip works correctly
+  app.set('trust proxy', 1);
+
   // Initialize logging
   const log = createLogger(config.LOG_LEVEL);
 
@@ -111,7 +125,7 @@ async function createApp() {
   licenseManager.loadSecret(config.LICENSE_SECRET_FILE);
 
   // HTTPS agent for internal CA
-  const CA_CERT_PATH = process.env.CA_CERT_PATH || '/app/pki/root.crt';
+  const CA_CERT_PATH = process.env.CA_CERT_PATH || platformPaths.pkiRootCert;
   let httpsAgent;
   try {
     const caCert = fs.readFileSync(CA_CERT_PATH);
@@ -380,6 +394,29 @@ async function createApp() {
   // Build versioned API router
   const apiRouter = express.Router();
 
+  // Version endpoint — public, no auth required
+  // Reads version from package.json at startup so the response always matches the running code
+  let appVersion = '0.0.0';
+  let appName = 'dashcaddy-api';
+  try {
+    const pkg = require('../package.json');
+    appVersion = pkg.version || appVersion;
+    appName = pkg.name || appName;
+  } catch { /* package.json unreadable — keep fallback */ }
+  apiRouter.get('/version', (req, res) => {
+    res.json({
+      success: true,
+      name: appName,
+      version: appVersion,
+      node: process.version,
+      platform: process.platform,
+      arch: process.arch,
+      uptime: process.uptime(),
+      instanceId: process.env.DASHCADDY_INSTANCE_ID || null
+    });
+  });
+  log.info('app', `Version endpoint available at /api/v1/version (v${appVersion})`);
+
   // Wire up notification listeners for resourceMonitor and backupManager
   if (ctx.notification && ctx.resourceMonitor) {
     ctx.resourceMonitor.on('alert', (alertData) => {