feat(keycloak): audience mapper for forte-drop-mcp on forte-cli (fallback)

Adds an oidc-audience-mapper to the forte-cli client so its access
tokens carry aud=https://mcp.drop.forteapps.net/mcp, the audience the
forte-drop-mcp auth sidecar verifies. Fallback for the case where
Keycloak ignores the RFC 8707 resource= parameter the skill sends.
Stacks on #26.

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

infra/values/base/keycloak-values.yaml

@@ -200,7 +200,21 @@ keycloakConfigCli:
             "webOrigins": [],
             "attributes": {
               "oauth2.device.authorization.grant.enabled": "true"
-            }
+            },
+            "protocolMappers": [
+              {
+                "name": "audience-forte-drop-mcp",
+                "protocol": "openid-connect",
+                "protocolMapper": "oidc-audience-mapper",
+                "consentRequired": false,
+                "config": {
+                  "included.custom.audience": "https://mcp.drop.forteapps.net/mcp",
+                  "access.token.claim": "true",
+                  "id.token.claim": "false",
+                  "introspection.token.claim": "true"
+                }
+              }
+            ]
           }
         ],
         "browserFlow": "browser-auto-idp",