docs: document DOMAIN_BRANDING env var in examples and README #332

.env.example

@@ -225,6 +225,29 @@ LOGIN_COMPANY_NAME=Bulwark Webmail
 # URL for the company website link on the login page.
 LOGIN_WEBSITE_URL=https://bulwarkmail.org
 
+# ---------------------------------------------------------------------------
+# Per-domain branding overrides (optional)
+# ---------------------------------------------------------------------------
+#
+# When you serve the webmail on multiple hostnames, each hostname can override
+# a subset of branding fields. Unset fields fall back to the global values
+# above. Match is on the request's Host (or X-Forwarded-Host) header.
+#
+# Use the leftmost label "*." to match any subdomain (e.g. "*.example.com"
+# matches mail.example.com and any deeper subdomain, but NOT example.com).
+# Exact matches always win over wildcards; the longest wildcard suffix wins
+# among multiple wildcard matches.
+#
+# Overridable keys: appName, appShortName, appDescription, faviconUrl,
+# pwaIconUrl, pwaThemeColor, pwaBackgroundColor, appLogoLightUrl,
+# appLogoDarkUrl, loginLogoLightUrl, loginLogoDarkUrl, loginCompanyName,
+# loginImprintUrl, loginPrivacyPolicyUrl, loginWebsiteUrl.
+#
+# Prefer setting this from the admin dashboard (PATCH /api/admin/config).
+# The env-var form is provided for stateless deployments.
+#
+# DOMAIN_BRANDING=[{"host":"maildomain1.com","loginCompanyName":"Company One","loginLogoLightUrl":"/branding/one-color.svg","loginLogoDarkUrl":"/branding/one-white.svg","loginWebsiteUrl":"https://one.example"},{"host":"maildomain2.com","loginCompanyName":"Company Two","faviconUrl":"/branding/two-favicon.svg"},{"host":"*.intranet.example.com","loginCompanyName":"Internal"}]
+
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