Set the chart's placeholder version to 0.50.0

Cosmetic: make helm-package passes --version and --app-version from the
tag, so these fields decide nothing about what is published. They are kept
in step so the tree heading for v0.50.0 does not say 0.49.1, as in
the 0.49.1 placeholder commit and 12535e0.

Claude-Session: https://claude.ai/code/session_016mBLURvJoMuUEr9cB2RpUN

charts/terdut-server/Chart.yaml

@@ -15,5 +15,5 @@ type: application
 # appVersion and image.tag in values.yaml no longer agree, and that is not an oversight:
 # image.tag stays "latest", which is what a local install actually pulls. appVersion is
 # metadata and drives nothing.
-version: 0.49.1
-appVersion: "v0.49.1"
+version: 0.50.0
+appVersion: "v0.50.0"