Phase 1: lock cron, reload chaud, argon2, providers, IMDb lookup, cache LRU, /health, /metrics, rate limit, UI dark, biome

lib/lockFile.js

@@ -0,0 +1,60 @@
+// Simple PID-based lock file. Atomic via O_EXCL.
+// If a stale lock is found (PID no longer alive), it is removed.
+
+import { closeSync, openSync, readFileSync, unlinkSync, writeSync } from 'node:fs';
+
+function isAlive(pid) {
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (e) {
+    return e.code === 'EPERM';
+  }
+}
+
+export function acquireLock(lockPath) {
+  for (let attempt = 0; attempt < 2; attempt++) {
+    try {
+      const fd = openSync(lockPath, 'wx');
+      writeSync(fd, String(process.pid));
+      closeSync(fd);
+      const release = () => {
+        try {
+          unlinkSync(lockPath);
+        } catch {
+          /* ignore */
+        }
+      };
+      process.on('exit', release);
+      process.on('SIGINT', () => {
+        release();
+        process.exit(130);
+      });
+      process.on('SIGTERM', () => {
+        release();
+        process.exit(143);
+      });
+      return release;
+    } catch (err) {
+      if (err.code !== 'EEXIST') throw err;
+      // Lock exists — check if owner is still alive
+      let pid = 0;
+      try {
+        pid = parseInt(readFileSync(lockPath, 'utf8').trim(), 10);
+      } catch {
+        /* unreadable */
+      }
+      if (pid && isAlive(pid)) {
+        throw new Error(`Cron already running (PID ${pid}, lock ${lockPath})`);
+      }
+      // Stale lock — remove and retry
+      console.log(`Removing stale lock (PID ${pid || '?'} no longer alive): ${lockPath}`);
+      try {
+        unlinkSync(lockPath);
+      } catch {
+        /* ignore */
+      }
+    }
+  }
+  throw new Error(`Could not acquire lock after retries: ${lockPath}`);
+}