Fix European trip return heuristic for weekend location tracking

Adjust European short trip heuristic from >3 days to >1 day to correctly
detect when user has returned home from European trips. This fixes the
April 29-30, 2023 case where the location incorrectly showed "Sankt Georg, Hamburg"
instead of "Bristol" when the user was free (no events scheduled) after
the foss-north trip ended on April 27.

The previous logic required more than 3 days to pass before assuming
return home from European countries, but for short European trips by
rail/ferry, users typically return within 1-2 days.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

node_modules/schema-utils/dist/keywords/undefinedAsNull.js

@@ -0,0 +1,37 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+/** @typedef {import("ajv").default} Ajv */
+/** @typedef {import("ajv").SchemaValidateFunction} SchemaValidateFunction */
+/** @typedef {import("ajv").AnySchemaObject} AnySchemaObject */
+/** @typedef {import("ajv").ValidateFunction} ValidateFunction */
+
+/**
+ *
+ * @param {Ajv} ajv
+ * @returns {Ajv}
+ */
+function addUndefinedAsNullKeyword(ajv) {
+  ajv.addKeyword({
+    keyword: "undefinedAsNull",
+    before: "enum",
+    modifying: true,
+    /** @type {SchemaValidateFunction} */
+    validate(kwVal, data, metadata, dataCxt) {
+      if (kwVal && dataCxt && metadata && typeof metadata.enum !== "undefined") {
+        const idx = dataCxt.parentDataProperty;
+        if (typeof dataCxt.parentData[idx] === "undefined") {
+          // eslint-disable-next-line no-param-reassign
+          dataCxt.parentData[dataCxt.parentDataProperty] = null;
+        }
+      }
+      return true;
+    }
+  });
+  return ajv;
+}
+var _default = addUndefinedAsNullKeyword;
+exports.default = _default;