Add CNAME file to enable www subdomain support

DNS_CONFIGURATION.md

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+# DNS Configuration for bemanproject.org
+
+This document describes the DNS configuration required to make both `bemanproject.org` and `www.bemanproject.org` work correctly with GitHub Pages.
+
+## Overview
+
+The repository now includes a `CNAME` file in the `static/` directory that contains `bemanproject.org`. This file is automatically copied to the root of the build output during the build process and is used by GitHub Pages to configure the custom domain.
+
+## Required DNS Configuration
+
+To enable both the apex domain (`bemanproject.org`) and the www subdomain (`www.bemanproject.org`), the following DNS records must be configured with your DNS provider (Gandi.net):
+
+### 1. A Records for Apex Domain (bemanproject.org)
+
+Create **four A records** pointing the apex domain to GitHub Pages IP addresses:
+
+```
+Host: @
+Type: A
+Value: 185.199.108.153
+
+Host: @
+Type: A
+Value: 185.199.109.153
+
+Host: @
+Type: A
+Value: 185.199.110.153
+
+Host: @
+Type: A
+Value: 185.199.111.153
+```
+
+### 2. CNAME Record for www Subdomain
+
+Create a **CNAME record** pointing the www subdomain to the GitHub Pages default domain:
+
+```
+Host: www
+Type: CNAME
+Value: bemanproject.github.io
+```
+
+**Important:** The CNAME record should point to `bemanproject.github.io` (without any path or repository name).
+
+## How It Works
+
+Once both the CNAME file in the repository and the DNS records are configured:
+
+1. GitHub Pages will automatically handle redirects between `bemanproject.org` and `www.bemanproject.org`
+2. Accessing `www.bemanproject.org` will work correctly and redirect to `bemanproject.org` (or vice versa)
+3. HTTPS will be available on both domains (may take up to 24 hours for certificate provisioning)
+
+## DNS Propagation
+
+DNS changes can take up to 24 hours to propagate globally. After configuring the DNS records, you can verify the configuration using these commands:
+
+### Verify A Records
+```bash
+dig bemanproject.org +noall +answer -t A
+```
+
+Expected output:
+```
+bemanproject.org    3600    IN A     185.199.108.153
+bemanproject.org    3600    IN A     185.199.109.153
+bemanproject.org    3600    IN A     185.199.110.153
+bemanproject.org    3600    IN A     185.199.111.153
+```
+
+### Verify CNAME Record
+```bash
+dig www.bemanproject.org +noall +answer -t CNAME
+```
+
+Expected output:
+```
+www.bemanproject.org    3600    IN CNAME    bemanproject.github.io.
+```
+
+## References
+
+- [GitHub Pages: Managing a custom domain](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/managing-a-custom-domain-for-your-github-pages-site#configuring-an-apex-domain-and-the-www-subdomain-variant)
+- [GitHub Pages: About custom domains](https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/about-custom-domains-and-github-pages)
+
+## GitHub Pages Settings
+
+After DNS configuration is complete, verify in the repository settings:
+
+1. Go to Settings → Pages
+2. Verify that "Custom domain" shows `bemanproject.org`
+3. Wait for DNS check to complete (green checkmark)
+4. Enable "Enforce HTTPS" (may take up to 24 hours to become available)

static/CNAME

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+bemanproject.org