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

docs/self-hosting/vercel.md

@@ -18,20 +18,24 @@ Fork [bentopdf/bentopdf](https://github.com/alam00000/bentopdf) to your GitHub a
 2. Select your forked repository
 3. Configure the project:
 
-| Setting | Value |
-|---------|-------|
-| Framework Preset | Vite |
-| Build Command | `npm run build` |
-| Output Directory | `dist` |
-| Install Command | `npm install` |
+| Setting          | Value           |
+| ---------------- | --------------- |
+| Framework Preset | Vite            |
+| Build Command    | `npm run build` |
+| Output Directory | `dist`          |
+| Install Command  | `npm install`   |
 
 ### Step 3: Environment Variables (Optional)
 
 Add these if needed:
 
-```
-SIMPLE_MODE=false
-```
+| Variable                | Description                                                 |
+| ----------------------- | ----------------------------------------------------------- |
+| `SIMPLE_MODE`           | Set to `true` for minimal UI                                |
+| `VITE_BRAND_NAME`       | Custom brand name (replaces "BentoPDF")                     |
+| `VITE_BRAND_LOGO`       | Logo path relative to `public/` (e.g. `images/my-logo.svg`) |
+| `VITE_FOOTER_TEXT`      | Custom footer/copyright text                                |
+| `VITE_DEFAULT_LANGUAGE` | Default UI language (e.g. `fr`, `de`, `es`)                 |
 
 ### Step 4: Deploy
 
@@ -73,3 +77,46 @@ Add a `vercel.json` for SPA routing:
   "rewrites": [{ "source": "/(.*)", "destination": "/index.html" }]
 }
 ```
+
+### Word/ODT/Excel to PDF Not Working
+
+LibreOffice WASM conversions require `SharedArrayBuffer`, which needs these response headers on all pages:
+
+- `Cross-Origin-Embedder-Policy: require-corp`
+- `Cross-Origin-Opener-Policy: same-origin`
+
+The pre-compressed `.wasm.gz` and `.data.gz` files also need `Content-Encoding: gzip` so the browser decompresses them.
+
+Add these to your `vercel.json`:
+
+```json
+{
+  "rewrites": [{ "source": "/(.*)", "destination": "/index.html" }],
+  "headers": [
+    {
+      "source": "/(.*)",
+      "headers": [
+        { "key": "Cross-Origin-Embedder-Policy", "value": "require-corp" },
+        { "key": "Cross-Origin-Opener-Policy", "value": "same-origin" },
+        { "key": "Cross-Origin-Resource-Policy", "value": "cross-origin" }
+      ]
+    },
+    {
+      "source": "/libreoffice-wasm/soffice.wasm.gz",
+      "headers": [
+        { "key": "Content-Type", "value": "application/wasm" },
+        { "key": "Content-Encoding", "value": "gzip" }
+      ]
+    },
+    {
+      "source": "/libreoffice-wasm/soffice.data.gz",
+      "headers": [
+        { "key": "Content-Type", "value": "application/octet-stream" },
+        { "key": "Content-Encoding", "value": "gzip" }
+      ]
+    }
+  ]
+}
+```
+
+To verify, open DevTools Console and run `console.log(window.crossOriginIsolated)` — it should return `true`.