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

.env.example

@@ -15,3 +15,10 @@ VITE_WASM_CPDF_URL=https://cdn.jsdelivr.net/npm/coherentpdf/dist/
 # Default UI language (build-time)
 # Supported: en, ar, be, fr, de, es, zh, zh-TW, vi, tr, id, it, pt, nl, da
 VITE_DEFAULT_LANGUAGE=
+
+# Custom branding (build-time)
+# Replace the default BentoPDF branding with your own.
+# Place your logo file in the public/ folder and set the path relative to it.
+VITE_BRAND_NAME=
+VITE_BRAND_LOGO=
+VITE_FOOTER_TEXT=