Add Reusable Notebook for Event-Based GTFS TDQ Analysis

[fsalemi]

Summary

This PR adds a reusable analysis tool that identifies bus and rail
transit stops near any venue and displays interactive maps and
summary tables.

ref: #2058

Structure

transit_event_analysis/
├── analysis.ipynb # Main notebook — open and run this
├── refresh_data.ipynb # Run this to fetch fresh data from BigQuery
├── query.sql # BigQuery SQL used to fetch stops data
├── df_dim_stops_latest.parquet # Pre-fetched stops data
├── utils/
│ └── geo_functions.py # All analysis logic
└── README.md

How to Use

1. Open analysis.ipynb in JupyterHub
2. Click Run → Run All Cells
3. Type a venue name and click ▶ Run Analysis
4. Interactive maps and summary tables will appear below

Notes

• To refresh the data in the future, run refresh_data.ipynb
• All heavy logic lives in utils/geo_functions.py — the notebook
  itself is minimal and user-friendly

[github-actions]

nbviewer URLs for impacted notebooks:

• transit_event_analysis/analysis.ipynb
• transit_event_analysis/refresh_data.ipynb