Update API endpoint and implement path prefix handling in the application

This commit modifies the API endpoint in `config.json` from `/api` to `/fcapi`, reflecting a change in the backend structure. Additionally, it introduces a new function in `src/index.js` to derive the API path prefix from the updated configuration, ensuring that requests are correctly routed when the API is served under a specific path. The application now logs the API path prefix during initialization, enhancing visibility into the routing configuration.

config.json

@@ -23,7 +23,7 @@
     "app": {
       "urlClient": "https://dev.tombutcher.work",
       "urlElectronClient": "http://localhost:5780",
-      "urlApi": "https://dev.tombutcher.work/api",
+      "urlApi": "https://dev.tombutcher.work/fcapi",
       "devAuthClient": "http://localhost:3500",
       "jenkinsProject": "https://ci.tombutcher.work/job/farmcontrol/job/farmcontrol-ui",
       "appUpdateStorage": "https://dist.farmcontrol.app/jenkins/farmcontrol/farmcontrol-ui"

src/index.js

@@ -91,6 +91,22 @@ const app = express();
 const logger = log4js.getLogger('App');
 logger.level = config.server.logLevel;
 
+// Public path prefix from app.urlApi (e.g. https://host/fcapi -> /fcapi).
+// Empty when the API is served at the host root. Requests that still carry
+// the prefix (reverse proxy did not strip it) are rewritten before routing.
+function apiPathPrefix() {
+  const urlApi = config.app?.urlApi;
+  if (!urlApi) return '';
+  try {
+    const pathname = new URL(urlApi).pathname.replace(/\/+$/, '');
+    return pathname && pathname !== '/' ? pathname : '';
+  } catch {
+    return '';
+  }
+}
+
+const API_PREFIX = apiPathPrefix();
+
 app.use(log4js.connectLogger(logger, { level: 'trace' }));
 
 const allowedOrigins = [
@@ -119,6 +135,7 @@ async function initializeApp() {
   logger.info(`Environment: ${getEnvironment()}`);
   logger.info(`Port: ${PORT}`);
   logger.info(`Log Level: ${config.server.logLevel}`);
+  logger.info(`API path prefix: ${API_PREFIX || '(none)'}`);
   try {
     // Connect to database
     await dbConnect();
@@ -174,6 +191,21 @@ app.use(
 app.use(express.json());
 app.use(populateUserMiddleware);
 
+if (API_PREFIX) {
+  app.use((req, _res, next) => {
+    const url = req.url || '/';
+    const matches =
+      url === API_PREFIX ||
+      url.startsWith(`${API_PREFIX}/`) ||
+      url.startsWith(`${API_PREFIX}?`);
+    if (matches) {
+      const stripped = url.slice(API_PREFIX.length);
+      req.url = stripped === '' ? '/' : stripped;
+    }
+    next();
+  });
+}
+
 app.get('/', function (req, res) {
   const __dirname = fs.realpathSync('.');
   res.sendFile(path.join(__dirname, '/src/landing/index.html'));