Add file watcher service for auto-importing XML invoices

Watches a configured folder for new .xml files using chokidar,
imports existing files on startup, and auto-imports newly added files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/services/watcher.js

@@ -0,0 +1,48 @@
+const chokidar = require('chokidar');
+const path = require('path');
+const fs = require('fs');
+const { importXmlFile } = require('./import-service');
+
+function startWatcher(db, folderPath) {
+  if (!fs.existsSync(folderPath)) {
+    fs.mkdirSync(folderPath, { recursive: true });
+  }
+
+  // Import existing XMLs first
+  const existingFiles = fs.readdirSync(folderPath)
+    .filter(f => f.toLowerCase().endsWith('.xml'))
+    .map(f => path.join(folderPath, f));
+
+  let imported = 0;
+  let skipped = 0;
+  for (const file of existingFiles) {
+    const result = importXmlFile(db, file);
+    if (result.success) imported++;
+    else skipped++;
+  }
+  console.log(`Initial scan: ${imported} imported, ${skipped} skipped`);
+
+  // Watch for new files
+  const watcher = chokidar.watch(path.join(folderPath, '*.xml'), {
+    persistent: true,
+    ignoreInitial: true,
+    awaitWriteFinish: {
+      stabilityThreshold: 2000,
+      pollInterval: 100,
+    },
+  });
+
+  watcher.on('add', (filePath) => {
+    console.log(`New XML detected: ${path.basename(filePath)}`);
+    const result = importXmlFile(db, filePath);
+    if (result.success) {
+      console.log(`  Imported: ${result.uuid}`);
+    } else {
+      console.log(`  Skipped: ${result.reason}`);
+    }
+  });
+
+  return watcher;
+}
+
+module.exports = { startWatcher };