feat: add SSO environment variables to docker-compose.yml and create .env.example

.env.example

@@ -0,0 +1,21 @@
+# JWT Secret used for admin/user authentication tokens (change this to a secure random value)
+JWT_SECRET=your_jwt_secret_here
+
+# SQLite Database path inside container (normally persistent volume, no need to change)
+# FULLS_DIR=/app/public/images/fulls
+# THUMBS_DIR=/app/public/images/thumbs
+
+# ==========================================
+# Keycloak SSO (OIDC) Configuration
+# ==========================================
+# Base Keycloak URL Realm Authority
+SSO_AUTHORITY=https://auth.mischlabs.de/realms/mischlabs
+
+# Client ID configured in Keycloak for Photography
+SSO_CLIENT_ID=pocketbase
+
+# Client Secret retrieved from Keycloak (Credentials tab)
+SSO_CLIENT_SECRET=
+
+# Public callback URI registered in Keycloak for the Photography app
+SSO_REDIRECT_URI=https://tom.mischlabs.de/api/auth/sso/callback