Session-level registry of active NavigationManager instances

[marioserrano09]

Part of #107. Phase 2 — depends on #109 (instance identity).

Goal

Allow a host shell (non-ZK front-end embedding multiple ZK iframes, or a future real-multi-tab UI) to enumerate, query, and target navigation for a specific open tab/iframe within the current HTTP session, instead of only being able to act on the implicit "current" manager resolved from ZK's execution context.

Scope

• New session-scoped registry (e.g. NavigationManagerRegistry, @Scope("session")) that tracks active NavigationManager instances by their id (Add stable instance identity to NavigationManager #109), registering on desktop/manager creation and removing on desktop destroy/session cleanup.
• API to list active instances and their current page for the session.
• Out of scope for this issue: any REST/SDK endpoint exposing this externally — evaluate need separately once the registry exists.

Affected modules

• platform/core/navigation
• platform/ui/zk (registration/deregistration hooks on desktop lifecycle)

[marioserrano09]

Implemented on branch feat/navigation-multi-desktop-support (commit 2a4246e): added NavigationManagerRegistry (@Scope("session")) tracking active instances by id. BaseNavigationManager self-registers on construction (null-safe outside a Spring context). ZKNavigationManager.init() wires best-effort unregistration via a ZK DesktopCleanup listener on the current desktop when it's destroyed. Correctness doesn't depend on that cleanup firing, since the registry is itself session-scoped and is discarded with the whole session — the cleanup listener is purely to keep the registry accurate while the session is still alive (e.g. one of several open iframes/tabs is closed).

[marioserrano09]

Implemented on feat/navigation-multi-desktop-support (commits 2a4246e, 0b2b831); PR #112. Will close with the PR.

[marioserrano09]

Implementado y mergeado en #112 (cd0e6dd en main). Cerrado. Pendiente a nivel épica (#107): validación contra dynamia-erp con login real de Spring Security y documentar el contrato de hand-off en docs/backend/.