Server 2.6.1: code field upper-cases and inserts the dash

The phone pages' code field gets one inline script, allowed by its
SHA-256 hash in the CSP; a test checks the served script against the
header. Image pinned by digest in k8s/server.yaml (not applied).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

k8s/server.yaml

@@ -29,8 +29,8 @@ spec:
           type: RuntimeDefault
       containers:
         - name: server
-          # 2.6.0, pinned by digest so a re-pushed tag cannot change what runs.
-          image: git.stinnesbeck.com/nils/mg4-server@sha256:35ff5973836620c1e69f06b00163cf95183f938cb9830355452d4161c6c46e33
+          # 2.6.1, pinned by digest so a re-pushed tag cannot change what runs.
+          image: git.stinnesbeck.com/nils/mg4-server@sha256:df1d40e423b7ee365e8379e2eaefb4c0db3a599e6429728a37d46827f83d82cd
           ports:
             - name: http
               containerPort: 8080