feat: Add APP_NAME env support for branding and deployment

- Make app name configurable via APP_NAME env variable - Update UI,
HTML, Docker, scripts, and k8s to use APP_NAME - Add process-html.sh for
template substitution - Document APP_NAME usage in
docs/APP_NAME_CONFIGURATION.md - Update Dockerfile, compose, and scripts
for dynamic naming - Add index.html.template for environment-based
branding

k8s/frontend-deployment.yaml.template

@@ -19,7 +19,7 @@ spec:
     spec:
       containers:
         - name: frontend
-          image: gitea-http.taildb3494.ts.net/will/meds:latest
+          image: ${DOCKER_IMAGE:-gitea-http.taildb3494.ts.net/will/${APP_NAME}:latest}
           ports:
             - containerPort: 80
           envFrom: