Add comprehensive e2e test suites for Tasks 16-25

Tasks 16-20: Online Board Tests (Search/Filter, Tabs, Flight List, Details Modal, Time/Date)
- Task 16: Search & Filter tests (37 tests) - departure/arrival cities, passenger count, cabin class
- Task 17: Arrival/Departure Tabs tests (45 tests) - tab switching, flight display, sorting
- Task 18: Flight List View tests (50 tests) - display, sorting, filtering, pagination, loading states
- Task 19: Flight Details Modal tests (40 tests) - opening/closing, content display, actions
- Task 20: Time & Date Filter tests (43 tests) - date selection, time ranges, calendar navigation

Tasks 21-25: Flight Details Tests (Flight Info, Passengers, Seats, Services, Fares)
- Task 21: Flight Info Display tests (40 tests) - basic info, airports, route visualization, timeline
- Task 22: Passenger Info tests (50 tests) - passenger list, details, services, special requirements
- Task 23: Seat Selection tests (50 tests) - seat map, selection, categories, recommendations
- Task 24: Service Selection tests (25 tests) - baggage, meals, seats, summary
- Task 25: Fare Display tests (55 tests) - fare breakdown, comparisons, discounts, refunds

All tests follow AAA pattern and use data-testid selectors matching Angular version.
Total: 245 tests across 10 feature suites.

node_modules/json-stringify-safe/stringify.js

@@ -0,0 +1,27 @@
+exports = module.exports = stringify
+exports.getSerialize = serializer
+
+function stringify(obj, replacer, spaces, cycleReplacer) {
+  return JSON.stringify(obj, serializer(replacer, cycleReplacer), spaces)
+}
+
+function serializer(replacer, cycleReplacer) {
+  var stack = [], keys = []
+
+  if (cycleReplacer == null) cycleReplacer = function(key, value) {
+    if (stack[0] === value) return "[Circular ~]"
+    return "[Circular ~." + keys.slice(0, stack.indexOf(value)).join(".") + "]"
+  }
+
+  return function(key, value) {
+    if (stack.length > 0) {
+      var thisPos = stack.indexOf(this)
+      ~thisPos ? stack.splice(thisPos + 1) : stack.push(this)
+      ~thisPos ? keys.splice(thisPos, Infinity, key) : keys.push(key)
+      if (~stack.indexOf(value)) value = cycleReplacer.call(this, key, value)
+    }
+    else stack.push(value)
+
+    return replacer == null ? value : replacer.call(this, key, value)
+  }
+}