Merge branch 'items'

src/tjts5901/app.py

src/tjts5901/items.py

src/tjts5901/models.py

src/tjts5901/templates/base.html

src/tjts5901/templates/items/index.html

src/tjts5901/templates/items/sell.html

src/tjts5901/templates/items/update.html

src/tjts5901/views.py