feat(frontend): système de plugins — runtime, menus, layouts custom (#43)

Lots F1-F4 : runtime de chargement/registre plugin, extension des menus
existants, panneau de gestion des plugins, types de layout custom
(sélecteur, fallback, cellule dédiée) branchés sur le port plugin.
Suite npm typecheck/test verte (947/947).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/features/settings/SettingsView.tsx

@@ -24,16 +24,18 @@
 import { Button, cn } from "@/shared";
 import { ProfilesSettings } from "@/features/first-run";
 import { DevicesScreen } from "@/features/devices";
+import { PluginsPanel } from "@/features/plugins";
 import { DeploymentSettings } from "./DeploymentSettings";
 
 /** The Settings sections, in menu/nav order. */
-export type SettingsSection = "aiProfiles" | "deployment" | "devices";
+export type SettingsSection = "aiProfiles" | "deployment" | "devices" | "plugins";
 
 /** Human labels, shared by the nav column and the `Settings` menu (ticket #78 — French). */
 export const SETTINGS_SECTION_LABEL: Record<SettingsSection, string> = {
   aiProfiles: "Profils IA",
   deployment: "Déploiement",
   devices: "Appareils",
+  plugins: "Plugins",
 };
 
 /** Section order — the single source of truth for both nav and menu. */
@@ -41,6 +43,7 @@ export const SETTINGS_SECTIONS: SettingsSection[] = [
   "aiProfiles",
   "deployment",
   "devices",
+  "plugins",
 ];
 
 interface SettingsViewProps {
@@ -93,6 +96,8 @@ export function SettingsView({
             <ProfilesSettings />
           ) : section === "deployment" ? (
             <DeploymentSettings />
+          ) : section === "plugins" ? (
+            <PluginsPanel />
           ) : (
             // No `onSessionEnded`: the desktop app hosts the server and is never
             // itself a paired device, so it cannot revoke its own session.