Add single-binary build and --port flag

bun build --compile bundles the app and Bun runtime into bin/job-board
(plus linux-x64/arm64 targets). New src/main.ts entry: serve (default)
or 'scrape' once, with --port/-p overriding PORT. A compiled binary
stores its database in data/ next to the executable.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scrapper/src/main.ts

@@ -0,0 +1,41 @@
+// Entry point (also used by the compiled binary):
+//   job-board [serve] [--port <n>]   start the web server (scrapes every 24h)
+//   job-board scrape                 run all scrapers once and exit (exit code 1 if any failed)
+
+export {};
+
+const USAGE = "Usage: job-board [serve] [--port <n>] | job-board scrape";
+
+function fail(message: string): never {
+  console.error(`${message}\n${USAGE}`);
+  process.exit(2);
+}
+
+const args = process.argv.slice(2);
+let command: string | undefined;
+for (let i = 0; i < args.length; i++) {
+  const arg = args[i]!;
+  if (arg === "--port" || arg === "-p" || arg.startsWith("--port=")) {
+    const value = arg.startsWith("--port=") ? arg.slice("--port=".length) : args[++i];
+    const port = Number(value);
+    if (!Number.isInteger(port) || port < 1 || port > 65535) fail(`Invalid port "${value ?? ""}".`);
+    process.env.PORT = String(port); // read by server.ts; overrides the PORT env var
+  } else if (arg === "--help" || arg === "-h") {
+    console.log(USAGE);
+    process.exit(0);
+  } else if (!command && !arg.startsWith("-")) {
+    command = arg;
+  } else {
+    fail(`Unknown argument "${arg}".`);
+  }
+}
+
+if (command === "scrape") {
+  const { runAllScrapers } = await import("./scrape");
+  const results = await runAllScrapers();
+  process.exit(results.some((r) => r.error) ? 1 : 0);
+} else if (command === undefined || command === "serve") {
+  await import("./server");
+} else {
+  fail(`Unknown command "${command}".`);
+}