feat(vars): VarsService + vars:: SDK + config capabilities

Scripts can now read group-inherited config via vars::get(key) / vars::all().

- shared: VarsService trait (read-only get/all) + NoopVarsService; added as
  the 14th field on the Services bundle.
- manager-core: VarsServiceImpl resolves the calling app's config via
  config_resolver (derives app_id from cx.app_id; AppVarsRead-gated for
  authed principals, script-as-gate for anon).
- executor-core: vars:: Rhai bridge (get/all), registered in the SDK.
- authz: AppVarsRead/Write, GroupVarsRead/Write, GroupSecretsRead/Write
  capabilities (group caps resolve via the Phase-2 ancestor walk; the
  GroupSecretsRead human-read gate is group_admin-only, distinct from an
  app's runtime injection).
- wired VarsServiceImpl into the picloud binary; updated the executor-core
  test Services::new call sites.

386 manager-core lib tests green; clippy clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud/src/lib.rs

@@ -33,7 +33,7 @@ use picloud_manager_core::{
     PrincipalResolver, PubsubServiceImpl, RealtimeAuthorityImpl, RepoResolver, RouteAdminState,
     RouteRepository, SandboxCeiling, ScriptRepository, SecretsConfig, SecretsServiceImpl,
     SecretsState, SubscriberTokenConfig, TopicRepo, TopicsState, TriggerConfig, TriggerRepo,
-    TriggersState, UsersServiceConfig, UsersServiceImpl,
+    TriggersState, UsersServiceConfig, UsersServiceImpl, VarsServiceImpl,
 };
 use picloud_orchestrator_core::realtime::DEFAULT_GC_INTERVAL_SECS;
 use picloud_orchestrator_core::routing::{AppDomainTable, RouteTable};
@@ -322,6 +322,8 @@ pub async fn build_app(
         // under script-as-gate semantics.
         .with_authz(authz.clone()),
     );
+    let vars: Arc<dyn picloud_shared::VarsService> =
+        Arc::new(VarsServiceImpl::new(pool.clone(), authz.clone()));
     let services = Services::new(
         kv,
         docs,
@@ -336,6 +338,7 @@ pub async fn build_app(
         users.clone(),
         queue,
         invoke,
+        vars,
     );
     // v1.1.9: keep the invoke depth bound aligned with the dispatcher's
     // trigger-depth bound (same counter under the hood).