docs: add DVF data source, pipeline steps, and WTM methodology

docs: accurate architecture docs per level in challenge notebook

docs: add methodology details to each notebook level

docs: fix commune colors, optimize notebook size (10.6→2MB)

docs: execute challenge notebook with all map outputs

feat: government vector tiles, dept selection, fix section rendering

feat: add exploration & challenge notebooks, update aggregated data

docs: remove personal references from notebook, keep it professional

docs: add detailed explanations to early notebook sections

docs: add methodology analysis, price comparison, and challenge answers to notebook

update: notebook with temporal weighting, timing, residential only

feat: initial DVF data pipeline with 6-level price aggregation