feat: add custom branding, air-gapped deployment script, and updated self-hosting docs

Dockerfile.nonroot

@@ -36,6 +36,14 @@ ENV VITE_WASM_CPDF_URL=$VITE_WASM_CPDF_URL
 ARG VITE_DEFAULT_LANGUAGE
 ENV VITE_DEFAULT_LANGUAGE=$VITE_DEFAULT_LANGUAGE
 
+# Custom branding (e.g. VITE_BRAND_NAME=MyCompany VITE_BRAND_LOGO=my-logo.svg)
+ARG VITE_BRAND_NAME
+ARG VITE_BRAND_LOGO
+ARG VITE_FOOTER_TEXT
+ENV VITE_BRAND_NAME=$VITE_BRAND_NAME
+ENV VITE_BRAND_LOGO=$VITE_BRAND_LOGO
+ENV VITE_FOOTER_TEXT=$VITE_FOOTER_TEXT
+
 ENV NODE_OPTIONS="--max-old-space-size=3072"
 
 RUN npm run build:with-docs