fix(admin): address PR review feedback from all personas

Blockers resolved:
- localStorage key collision: UsersListPanel/GroupsListPanel/TagsListPanel
  now each use their own key (admin_*_list_collapsed)
- $effect autocollapse replaced with $derived(autocollapse || manualCollapse)
  across all three list panels (Felix — Svelte 5 rule violation)
- groups/new: add READ_ALL and ANNOTATE_ALL to available standard permissions
- Mobile back-to-list links added to all five detail panel headers (md:hidden)
  so users landing directly on a detail URL on mobile can navigate back
- onDestroy(() => stopPolling()) added to system/+page.svelte (Tobias)

High priority resolved:
- Permission labels in groups/[id] and groups/new now use Paraglide i18n keys
  (admin_perm_read_all, admin_perm_annotate_all, etc.) across de/en/es
- $derived used for permission arrays (reactive i18n) — Felix Svelte 5 rule
- UserGroup type in +layout.server.ts now uses generated API type (Markus/Felix)
- discardTarget annotation changed to variable-level type annotation

Accessibility (Leonie):
- EntityNav tablet icon strip buttons: min-h-[44px] for WCAG 2.5.8 compliance
- Flyout focus management: openFlyout() focuses first link, closeFlyout()
  returns focus to the trigger button that opened it
- Flyout animation replaced: broken inline style -> transition:fly={{ x: -160 }}

Tests (Sara/Felix):
- localStorage key assertion tests added per panel
- localStorage.removeItem calls updated to use the panel-specific keys
- page.server.spec.ts added for groups/[id] and tags/[id] delete actions
- Polling lifecycle tests added to system/page.svelte.spec.ts

Note: Paraglide types for new admin_perm_* keys regenerate automatically on
next npm run dev (Vite plugin). No manual compilation step needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/de.json

@@ -190,6 +190,13 @@
 	"admin_group_created": "Gruppe erstellt.",
 	"admin_groups_section_standard": "Standard",
 	"admin_groups_section_administrative": "Administrativ",
+	"admin_perm_read_all": "Nur lesen",
+	"admin_perm_annotate_all": "Lesen & Annotieren",
+	"admin_perm_write_all": "Lesen & Schreiben",
+	"admin_perm_admin": "Vollzugriff (Admin)",
+	"admin_perm_admin_user": "Benutzer verwalten",
+	"admin_perm_admin_tag": "Schlagworte verwalten",
+	"admin_perm_admin_permission": "Berechtigungen verwalten",
 	"admin_user_new_heading": "Neuen Benutzer anlegen",
 	"admin_user_edit_heading": "Benutzer bearbeiten: {username}",
 	"admin_user_created": "Benutzer wurde erstellt.",

frontend/messages/en.json

@@ -190,6 +190,13 @@
 	"admin_group_created": "Group created.",
 	"admin_groups_section_standard": "Standard",
 	"admin_groups_section_administrative": "Administrative",
+	"admin_perm_read_all": "Read only",
+	"admin_perm_annotate_all": "Read & Annotate",
+	"admin_perm_write_all": "Read & Write",
+	"admin_perm_admin": "Full access (Admin)",
+	"admin_perm_admin_user": "Manage users",
+	"admin_perm_admin_tag": "Manage tags",
+	"admin_perm_admin_permission": "Manage permissions",
 	"admin_user_new_heading": "Create new user",
 	"admin_user_edit_heading": "Edit user: {username}",
 	"admin_user_created": "User has been created.",

frontend/messages/es.json

@@ -190,6 +190,13 @@
 	"admin_group_created": "Grupo creado.",
 	"admin_groups_section_standard": "Est\u00e1ndar",
 	"admin_groups_section_administrative": "Administrativo",
+	"admin_perm_read_all": "Solo lectura",
+	"admin_perm_annotate_all": "Leer y anotar",
+	"admin_perm_write_all": "Leer y escribir",
+	"admin_perm_admin": "Acceso completo (Admin)",
+	"admin_perm_admin_user": "Gestionar usuarios",
+	"admin_perm_admin_tag": "Gestionar etiquetas",
+	"admin_perm_admin_permission": "Gestionar permisos",
 	"admin_user_new_heading": "Crear nuevo usuario",
 	"admin_user_edit_heading": "Editar usuario: {username}",
 	"admin_user_created": "Usuario creado.",