v3: added opengraph support to the app, wrote README instructions incl. a Docker image

.env.example

@@ -1,8 +1,31 @@
+# ── API server ────────────────────────────────────────────────────────────────
+
+# Protocol the API server listens on (http or https)
 GERBEUR_PROTOCOL=http
+
+# Public hostname for the API (used in generated URLs, e.g. OG image tags)
 GERBEUR_HOSTNAME=localhost
+
+# Network interface Oak binds to. Default: 0.0.0.0 (all interfaces, required for Docker).
+# Set to 127.0.0.1 to restrict to loopback only.
+GERBEUR_LISTEN_HOST=0.0.0.0
+
+# Port the API server listens on
 GERBEUR_PORT=8000
-JWT_SECRET=
+
+# Comma-separated list of origins allowed to make cross-origin requests.
+# In dev: Vite's dev server URL (check actual host/port in Vite output).
+# In prod (same container): your public domain.
+# Example: http://localhost:3000,http://127.0.0.1:3000
+GERBEUR_ALLOWED_ORIGINS=http://localhost:3000
+
+# Secret key used to sign JWTs. Generate with: openssl rand -hex 32
+GERBEUR_JWT_SECRET=
+
+# ── Frontend (Vite) ───────────────────────────────────────────────────────────
+# These must be prefixed with VITE_ to be exposed to the client bundle.
+# They tell the frontend where the API server is reachable from the browser.
 
 VITE_API_PROTOCOL=http
-VITE_SERVER_HOST=localhost
-VITE_SERVER_PORT=8000
+VITE_API_HOSTNAME=localhost
+VITE_API_PORT=8000