Add Flask shopping app with Nomad deployment

Flask app serving the Citti shopping list with SQLite persistence,
per-category item addition, dynamic custom categories, photo upload,
and a post-trip price analysis page.

- Port 9756, DATA_DIR env var for persistent volume in Nomad
- Gitea Actions pipeline builds Docker image and deploys via Nomad API
- Makefile targets: run, install, build, push

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,16 @@
+IMAGE ?= gea.i80.dk/hjess/citti
+TAG   ?= latest
+
+.PHONY: run install build push
+
+run:
+	python app.py
+
+install:
+	pip install -r requirements.txt
+
+build:
+	docker build -t $(IMAGE):$(TAG) .
+
+push: build
+	docker push $(IMAGE):$(TAG)