chore: derive version from git tags via hatch-vcs

Replace hardcoded version in pyproject.toml with hatch-vcs so the
package version is read from git tags at build time. Dockerfile
accepts a VERSION build arg and passes it as HATCH_VCS_PRETEND_VERSION
for builds without a git checkout. Makefile _tag target now rebuilds
the container with the correct version automatically.

Makefile

@@ -45,3 +45,27 @@ docker-clean:
 	docker system prune -f
 
 docker-restart: docker-down docker-up
+
+# Bump helpers — reads the latest semver tag and creates the next one.
+# If no tag exists yet, starts from v0.0.0.
+_LATEST := $(shell git tag --sort=-v:refname | grep -E '^v[0-9]+\.[0-9]+\.[0-9]+$$' | head -1)
+_BASE   := $(if $(_LATEST),$(_LATEST),v0.0.0)
+_MAJ    := $(shell echo $(_BASE) | sed 's/^v//' | cut -d. -f1)
+_MIN    := $(shell echo $(_BASE) | sed 's/^v//' | cut -d. -f2)
+_PAT    := $(shell echo $(_BASE) | sed 's/^v//' | cut -d. -f3)
+
+patch:
+	@NEW=v$(_MAJ).$(_MIN).$(shell expr $(_PAT) + 1); \
+	git tag $$NEW && echo "Tagged $$NEW" && $(MAKE) _tag TAG=$$NEW
+
+minor:
+	@NEW=v$(_MAJ).$(shell expr $(_MIN) + 1).0; \
+	git tag $$NEW && echo "Tagged $$NEW" && $(MAKE) _tag TAG=$$NEW
+
+major:
+	@NEW=v$(shell expr $(_MAJ) + 1).0.0; \
+	git tag $$NEW && echo "Tagged $$NEW" && $(MAKE) _tag TAG=$$NEW
+
+_tag:
+	git push origin $(TAG)
+	docker-compose build --no-cache --build-arg VERSION=$(TAG:v%=%)