fix: add missing migrateConfig method, config versioning, and formatters module

ConfigManager.migrateConfig() was called but never defined — would crash at runtime.
Added config version checking, migration support, and fixed createEndpoint indentation.
New formatters module (csv, influxdb, json) for pluggable output formatting.

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

src/helper/formatters/csvFormatter.js

@@ -0,0 +1,44 @@
+/**
+ * CSV formatter
+ * Produces a single CSV line: timestamp,measurement,field1=val1,field2=val2,...
+ *
+ * Values are escaped if they contain commas or quotes.
+ *
+ * @param {string} measurement - The measurement name (e.g. node name)
+ * @param {object} metadata    - { fields, tags }
+ *   - fields: key/value pairs of changed data points
+ *   - tags:   flat key/value string pairs (included as columns)
+ * @returns {string} CSV-formatted line
+ */
+function format(measurement, metadata) {
+  const { fields, tags } = metadata;
+  const timestamp = new Date().toISOString();
+  const parts = [escapeCSV(timestamp), escapeCSV(measurement)];
+
+  // Append tags first, then fields
+  if (tags) {
+    for (const key of Object.keys(tags).sort()) {
+      parts.push(escapeCSV(`${key}=${tags[key]}`));
+    }
+  }
+
+  for (const key of Object.keys(fields).sort()) {
+    parts.push(escapeCSV(`${key}=${fields[key]}`));
+  }
+
+  return parts.join(',');
+}
+
+/**
+ * Escapes a value for safe inclusion in a CSV field.
+ * Wraps in double quotes if the value contains a comma, quote, or newline.
+ */
+function escapeCSV(value) {
+  const str = String(value);
+  if (str.includes(',') || str.includes('"') || str.includes('\n')) {
+    return '"' + str.replace(/"/g, '""') + '"';
+  }
+  return str;
+}
+
+module.exports = { format };