fix(auth): separate Pireon clients for authorization code and password

Pireon OAuth clients allow a single grant type. With one PIREON_CLIENT_ID of
type password, email + password worked but "Sign in with Pireon" failed with
`unauthorized_client`.

- PIREON_CLIENT_ID/SECRET: authorization_code client (Sign in with Pireon,
  Swagger UI). New PIREON_PASSWORD_CLIENT_ID/SECRET: password client, falling
  back to the former so existing setups keep working.
- Refresh tries both clients: a refresh token only works with its issuer.
- PIREON_PASSWORD_GRANT=false now also rejects password grants in the API
  (before it only hid the form).
- /api/auth/config returns clientId: null when there is no authorization_code
  client, and the web hides "Sign in with Pireon".
- docker-compose passes the new variables; docs 05/07, .env.example,
  openapi.json; unit tests for the client selection.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/identity/application/src/lib/auth.store.ts

@@ -148,7 +148,7 @@ export const AuthStore = signalStore(
         redirectToPireon$: events.on(authPageEvents.signInWithPireon).pipe(
           exhaustMap(({ payload }) => {
             const config = store.config();
-            if (!config)
+            if (!config?.clientId)
               return [
                 authApiEvents.signInFailed(
                   'Pireon sign-in is not configured on the API',

libs/web/identity/domain/src/lib/session.ts

@@ -16,7 +16,8 @@ export interface CurrentUser {
 /** How the browser can sign in (null config = the API has no Pireon client yet). */
 export interface AuthConfig {
   authorizeUrl: string;
-  clientId: string;
+  /** Null when only email + password is configured (no "Sign in with Pireon"). */
+  clientId: string | null;
   scopes: string[];
   passwordGrant: boolean;
 }

libs/web/identity/infrastructure/src/lib/adapters/browser-authorization.flow.ts

@@ -21,6 +21,8 @@ export class BrowserAuthorizationFlow extends AuthorizationFlow {
   private readonly document = inject(DOCUMENT);
 
   async start(config: AuthConfig, returnUrl: string): Promise<void> {
+    if (!config.clientId)
+      throw new Error('Pireon sign-in is not configured on the API');
     const codeVerifier = randomString(64);
     const state = randomString(32);
     sessionStorage.setItem(

libs/web/identity/presenters/src/lib/pages/login.page.ts

@@ -163,7 +163,7 @@ const SAMPLE_FEED = [
             />
           }
 
-          @if (auth.config(); as config) {
+          @if (auth.config()?.clientId) {
             <pi-action-button
               size="w100"
               color="primary"
@@ -172,7 +172,7 @@ const SAMPLE_FEED = [
               [disabled]="busy()"
               (execute)="auth.signInWithPireon(returnUrl())"
             />
-            @if (config.passwordGrant) {
+            @if (passwordEnabled()) {
               <pi-divider color="grey" label="o" gap="m" />
             }
           }