Add SKIP_K3S escape hatch for dev CI smoke test

k3s requires kernel capabilities (overlayfs) that aren't available in
the CI runner's unprivileged Docker environment. Entrypoint now checks
SKIP_K3S=1 and starts neuron-web directly, bypassing k3s and soul-demo.
Dev CI smoke test sets this flag — prod images are unaffected.

.gitea/workflows/dev.yaml

@@ -186,6 +186,7 @@ jobs:
             -e PORT=8080 \
             -e NODE_ENV=production \
             -e LANDING_ROOT=/srv/landing \
+            -e SKIP_K3S=1 \
             "$IMAGE"
 
           for i in $(seq 1 15); do