docs: add docs for kubernetes deployment

docs/self-hosting/index.md

@@ -81,6 +81,7 @@ Choose your platform:
 - [Nginx](/self-hosting/nginx)
 - [Apache](/self-hosting/apache)
 - [Docker](/self-hosting/docker)
+- [Kubernetes](/self-hosting/kubernetes)
 - [CORS Proxy](/self-hosting/cors-proxy) - Required for digital signatures
 
 ## System Requirements

docs/self-hosting/kubernetes.md

@@ -0,0 +1,157 @@
+# Deploy with Kubernetes
+
+Kubernetes may be overkill for a static site, but it can be a great fit if you already standardize on Helm + GitOps.
+
+> [!IMPORTANT]
+> **Required Headers for Office File Conversion**
+> 
+> LibreOffice-based tools (Word, Excel, PowerPoint conversion) require these HTTP headers for `SharedArrayBuffer` support:
+> - `Cross-Origin-Opener-Policy: same-origin`
+> - `Cross-Origin-Embedder-Policy: require-corp`
+> 
+> The official BentoPDF nginx images include these headers. In Kubernetes, **Ingress/Gateway controllers are also reverse proxies**, so ensure these headers are preserved (or add them at the edge).
+
+## Prereqs
+
+- Kubernetes cluster
+- Helm v3
+- A BentoPDF nginx image (e.g. `ghcr.io/alam00000/bentopdf:<tag>`) that serves on **port 8080**
+
+## Deploy with Helm
+
+### Install from this repo (local chart)
+
+```bash
+kubectl create namespace bentopdf
+
+helm upgrade --install bentopdf /path/to/bentopdf/chart \
+  --namespace bentopdf \
+  --set image.repository=ghcr.io/alam00000/bentopdf \
+  --set image.tag=latest
+```
+
+### Install from GHCR (OCI chart)
+
+If the chart is published to GHCR as an OCI artifact:
+
+```bash
+export GHCR_USERNAME="<github-org-or-user>"
+
+helm upgrade --install bentopdf oci://ghcr.io/$GHCR_USERNAME/charts/bentopdf \
+  --namespace bentopdf \
+  --create-namespace \
+  --version 0.1.0 \
+  --set image.repository=ghcr.io/alam00000/bentopdf \
+  --set image.tag=latest
+```
+
+## Expose it
+
+### Port-forward (quick test)
+
+```bash
+kubectl -n bentopdf port-forward deploy/bentopdf 8080:8080
+```
+
+### Ingress (optional)
+
+Enable Ingress (example for nginx-ingress):
+
+```yaml
+ingress:
+  enabled: true
+  className: nginx
+  hosts:
+    - host: pdf.example.com
+      paths:
+        - path: /
+          pathType: Prefix
+```
+
+### Gateway API (optional)
+
+This chart supports Gateway API `Gateway` + `HTTPRoute`.
+
+Example (Cloudflare Gateway API operator):
+
+```yaml
+gateway:
+  enabled: true
+  name: bento-tunnel
+  namespace: bentopdf
+  gatewayClassName: cloudflare
+
+httpRoute:
+  enabled: true
+  parentRefs:
+    - name: bento-tunnel
+      namespace: bentopdf
+      sectionName: http
+  hostnames:
+    - pdfs.example.com
+```
+
+## Ensuring the SharedArrayBuffer headers still work (Ingress/Gateway)
+
+### What "should" happen
+
+BentoPDF’s nginx config sets the required response headers. Most Ingress/Gateway controllers **pass upstream response headers through unchanged**.
+
+### What can break it
+
+- A controller/edge policy that **overrides** or **strips** response headers
+- A "security headers" middleware that sets different COOP/COEP values
+
+### How to verify
+
+Run this against your public endpoint:
+
+```bash
+curl -I https://pdf.example.com/ | egrep -i 'cross-origin-opener-policy|cross-origin-embedder-policy'
+```
+
+You should see:
+
+- `Cross-Origin-Opener-Policy: same-origin`
+- `Cross-Origin-Embedder-Policy: require-corp`
+
+### If your Ingress controller does not preserve them
+
+Add the headers at the edge (controller-specific). Example for **nginx-ingress**:
+
+```yaml
+ingress:
+  enabled: true
+  className: nginx
+  annotations:
+    nginx.ingress.kubernetes.io/configuration-snippet: |
+      add_header Cross-Origin-Opener-Policy "same-origin" always;
+      add_header Cross-Origin-Embedder-Policy "require-corp" always;
+```
+
+### If you’re using Gateway API and want to force-add headers
+
+Gateway API supports a `ResponseHeaderModifier` filter. You can attach it in `httpRoute.rules[*].filters`:
+
+```yaml
+httpRoute:
+  enabled: true
+  hostnames: [pdf.example.com]
+  parentRefs:
+    - name: bento-tunnel
+      namespace: misc
+      sectionName: http
+  rules:
+    - matches:
+        - path: { type: PathPrefix, value: / }
+      filters:
+        - type: ResponseHeaderModifier
+          responseHeaderModifier:
+            set:
+              - name: Cross-Origin-Opener-Policy
+                value: same-origin
+              - name: Cross-Origin-Embedder-Policy
+                value: require-corp
+```
+
+Support for specific filters depends on your Gateway controller; if a filter is ignored, add headers at the edge/controller layer instead.