💡 What:

• Replaced nested loops and Object.values(railwayData).forEach with $O(1)$ Hash Map lookups inside TripsPage.tsx.
• Converted functional .forEach mapping into single-pass for...in loops with break conditions and Object.prototype.hasOwnProperty.call() checks in WalkTripEditor.tsx and GlobalSearchModal.tsx.

🎯 Why:
The codebase frequently processes a massive railwayData state object. Using Object.keys(), Object.values(), or Object.entries() creates huge temporary arrays that stress the garbage collector. Additionally, $O(N^2)$ iterations inside React render loops can cause UI thread blocking and lag.

📊 Impact:

• TripsPage: Reduces computational overhead from $O(\text{Trips} \times \text{Lines} \times \text{Stations})$ to $O(\text{Lines} \times \text{Stations} + \text{Trips})$ during re-renders, vastly improving page load time when viewing large trip histories.
• WalkTripEditor: Prevents full loop evaluation, immediately exiting when both startId and endId match.
• GlobalSearchModal: Prevents creating huge [lineKey, lineData] arrays on every keystroke, directly improving typing responsiveness.

🔬 Measurement:

• Ran npm run lint and npm run build locally successfully.
• No tests were broken (npx tsx test_find_station.ts passes).

PR created automatically by Jules for task 3680989735805471630 started by @OsakaLOOP