misc(readme): Update README to point to backend for setup instructions

misc(env): Update gitignore and example env

chore(netlify): Add redirects file

Update git clone URL in README

overhaul(assets): Replace old assets (#27)

refactor(structure): Simplify directory structure (#24)

refactor(queries): Standardise queries and tree data

refactor(queries): Remove old section tree fetcher and useQueries

refactor(queries): Switch current user to useSuspense

refactor(tree): Switch section page to use section tree

feat(tree): Add new section tree query and hook

refactor(queries): Switch to query options

refactor(batcher): Extract batcher logic into a batcherFactory

Update README

refactor(lesson button): Extract logic into hook