feat(modules): dynamic sidebar group rendering active modules

The sidebar gains a new section that lists each currently-activated module
as a direct shortcut to its settings page. This is the always-visible
companion to the company-context Active Modules index — both surface the
same set of modules, but the index is the catalog landing page and the
sidebar group is the per-module quick access.

- BootstrapController returns module_menu populated from
  \InvoiceShelf\Modules\Registry::allMenu(), but only on the company-context
  branch — not on the super-admin branch (lines 53-69), since super admins
  don't see the dynamic group. Because nwidart only boots service providers
  for currently-activated modules, the registry naturally contains only
  active modules at request time, no extra filtering needed.

- bootstrap.service.ts BootstrapResponse type extended with
  module_menu?: ModuleMenuItem[]; new ModuleMenuItem interface
  (title/link/icon) — shaped distinctly from MenuItem because module entries
  use namespaced i18n keys and don't carry group/ability metadata.

- global.store.ts exposes a moduleMenu ref + a hasActiveModules computed.

- SiteSidebar.vue appends a new "Modules" section after the existing
  menuGroups output, in both the mobile (Dialog) and desktop branches. The
  section is hidden when hasActiveModules is false. Uses the
  modules.sidebar.section_title i18n key added in the previous commit.

resources/scripts/api/services/bootstrap.service.ts

@@ -15,6 +15,20 @@ export interface MenuItem {
   ability?: string
 }
 
+/**
+ * Sidebar item registered by an active module via
+ * \InvoiceShelf\Modules\Registry::registerMenu() in the module's ServiceProvider::boot().
+ *
+ * Distinct shape from MenuItem because module entries are namespaced (i18n
+ * keys come from the module's lang files) and don't carry group/ability —
+ * they always render under the dynamic "Modules" sidebar section.
+ */
+export interface ModuleMenuItem {
+  title: string
+  link: string
+  icon: string
+}
+
 export interface BootstrapResponse {
   current_user: User
   current_user_settings: Record<string, string>
@@ -28,6 +42,7 @@ export interface BootstrapResponse {
   config: Record<string, unknown>
   global_settings: Record<string, string>
   modules: string[]
+  module_menu?: ModuleMenuItem[]
   admin_mode?: boolean
   pending_invitations?: Array<{
     token: string