fix: use correct health endpoint and HTTP method for server integration

ConnectivityHealthCheck: /actuator/health → /api/v1/health (actuator
now requires auth on cameleer3-server after OIDC was added).

Bootstrap: POST → PUT for /api/v1/admin/oidc (server expects PUT,
POST returned 405 causing OIDC config to silently fail).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/java/net/siegeln/cameleer/saas/observability/ConnectivityHealthCheck.java

@@ -30,7 +30,7 @@ public class ConnectivityHealthCheck {
                     .baseUrl(runtimeConfig.getCameleer3ServerEndpoint())
                     .build();
             var response = client.get()
-                    .uri("/actuator/health")
+                    .uri("/api/v1/health")
                     .retrieve()
                     .toBodilessEntity();
             if (response.getStatusCode().is2xxSuccessful()) {