chore(config): use generic placeholder URLs in the OIDC example (#329)

The EXTERNAL SSO / OIDC sample in .env.example hardcoded PGAN's pogoalerts.net
endpoints as the example provider. PoracleWeb is fully OIDC-provider-agnostic and
open source, so the example should not be branded to one deployment.

Replace the sample provider name and authorize/token/userinfo URLs with neutral
placeholders (My SSO / https://sso.example.com/...), generalize the intro to list
common providers (Keycloak, Authentik, Auth0, Okta), and add a note to swap in your
provider's real endpoints. The per-provider reference matrix (which carries no URLs)
is unchanged.

Author: hokiepokedad2

.env.example

@@ -78,15 +78,16 @@ TELEGRAM_ENABLED=false
 # ═══════════════════════════════════════════════════════════════════════════════
 # EXTERNAL SSO / OIDC (optional — delegate login to your own OAuth2/OIDC provider)
 # ═══════════════════════════════════════════════════════════════════════════════
-# Point PoracleWeb at any OAuth2/OIDC provider (e.g. PogoAlerts) for single sign-on.
+# Point PoracleWeb at any OAuth2/OIDC provider (Keycloak, Authentik, Auth0, Okta, …) for SSO.
 # The provider's userinfo endpoint must return a claim holding the user's Poracle id
 # (a Discord/Telegram id) — set OIDC_IDENTITY_CLAIM to that claim name.
 # Enabled is auto-inferred when ClientId + the three URLs are all set; set explicitly to override.
+# Replace the example URLs below with your provider's actual endpoints.
 # OIDC_ENABLED=true
-# OIDC_PROVIDER_NAME=PogoAlerts
-# OIDC_AUTHORIZATION_URL=https://pogoalerts.net/login
-# OIDC_TOKEN_URL=https://pogoalerts.net/api/oauth/token
-# OIDC_USERINFO_URL=https://pogoalerts.net/api/oauth/userinfo
+# OIDC_PROVIDER_NAME=My SSO
+# OIDC_AUTHORIZATION_URL=https://sso.example.com/authorize
+# OIDC_TOKEN_URL=https://sso.example.com/oauth/token
+# OIDC_USERINFO_URL=https://sso.example.com/oauth/userinfo
 # OIDC_CLIENT_ID=your_oidc_client_id
 # OIDC_CLIENT_SECRET=your_oidc_client_secret
 # OIDC_SCOPES=openid profile email