fix(dashboard): guard empty COZYSTACK_VERSION in the console APP_VERSION build-arg

Address non-blocking review feedback from lexfrei on
packages/system/dashboard/Makefile:34.

When COZYSTACK_VERSION is empty (a local build with no matching git tag) the
build-arg baked a bare `APP_VERSION=v` into the console bundle. Match the guard
the root Makefile already uses for platformVersion so an empty version yields an
empty APP_VERSION instead of "v". Dev-only cosmetics — the config.json path
overrides the displayed version at deploy time — but it removes the mismatch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>

packages/system/dashboard/Makefile

@@ -31,7 +31,7 @@ build-console:
 		$(call image-tags,cozystack-ui,v$(COZYSTACK_VERSION)) \
 		$(call cache-args,cozystack-ui) \
 		--metadata-file images/console.json \
-		--build-arg APP_VERSION=v$(COZYSTACK_VERSION) \
+		--build-arg APP_VERSION=$(if $(COZYSTACK_VERSION),v$(COZYSTACK_VERSION),) \
 		--push=$(PUSH) \
 		--label "org.opencontainers.image.source=https://github.com/cozystack/cozystack" \
 		--load=$(LOAD)