feat(web): disable Jitsi-watermark overlay in video feed

interface_config.js is shipped hardcoded by jitsi/web with
SHOW_JITSI_WATERMARK: true and there's no env-var override in the
upstream image. Patch via postStart lifecycle hook so the runtime-
rendered file gets sed'd after startup-templating finishes. nginx
serves the file fresh on every request, so the tiny race between
pod-ready and postStart completing is irrelevant in practice.

infra/k3s/50-web.yaml

@@ -21,6 +21,26 @@ spec:
             - secretRef: { name: jitsi-secrets }
           ports:
             - { name: http, containerPort: 80 }
+          # interface_config.js is rendered from /defaults at container
+          # startup. The Jitsi-logo overlay in the video tile is controlled
+          # by SHOW_JITSI_WATERMARK which is hardcoded to `true` upstream
+          # and not exposed as an env var. Patch the rendered file via
+          # postStart — runs after startup-templating; nginx re-serves the
+          # file from disk on every request so any tiny race is fine.
+          lifecycle:
+            postStart:
+              exec:
+                command:
+                  - /bin/sh
+                  - -c
+                  - |
+                    for i in $(seq 1 30); do
+                      [ -f /config/interface_config.js ] && break
+                      sleep 1
+                    done
+                    sed -i 's/SHOW_JITSI_WATERMARK: true/SHOW_JITSI_WATERMARK: false/' /config/interface_config.js
+                    sed -i "s|JITSI_WATERMARK_LINK: '[^']*'|JITSI_WATERMARK_LINK: ''|" /config/interface_config.js
+                    sed -i 's/SHOW_POWERED_BY: true/SHOW_POWERED_BY: false/' /config/interface_config.js
           readinessProbe:
             httpGet: { path: /, port: 80 }
             initialDelaySeconds: 10