feat(api): implement Flight Data Analysis solution (FastAPI + pandas)

Запрос на слияние 'spec' (#2) из spec в master

docs(demo,readme): add demo artefacts and update README (Variant 5)

upload files

chore: base requirements for Django + DRF + pandas

docs(dev): developer guide and contracts

docs(demo,readme): add demo artefacts and update README (Variant 5)

chore: base requirements for Django + DRF + pandas

docs(dev): developer guide and contracts

docs: add project README (Variant 5)

docs(demo): expected API examples for Variant 5

docs(spec): add codex.md for Variant 5 + sample dataset

chore: scaffold for Variant 5 (spec/demo/data)

chore: scaffold for Variant 5 (spec/demo/data)