feat(09-02): add frontend keyboard shortcut service, store, and controller

- Create keyboard-shortcut-service.ts singleton with keydown listener
- Shadow DOM active element resolution for scope detection
- Text input suppression (only Escape passes through)
- Scope resolution: text-input > panel-specific > global
- Action dispatch to player/queue stores and Wails bindings
- Create shortcuts-store.ts with Wails persistence and event sync
- Create shortcuts-controller.ts for Lit component integration
- Export store and controller from store/index.ts
- Replace hardcoded Ctrl+F handler in index.ts with service
- Initialize service via import in frontend/index.ts

frontend/src/store/controllers/shortcuts-controller.ts

@@ -0,0 +1,60 @@
+import type { ReactiveController, ReactiveControllerHost } from 'lit';
+import type { ShortcutsState } from '../shortcuts-store';
+import { shortcutsStore } from '../shortcuts-store';
+
+/**
+ * ShortcutsController connects a Lit component to the ShortcutsStore.
+ *
+ * Use this controller in components that need to read or change
+ * shortcut bindings (e.g. the shortcut settings UI in config-page).
+ */
+export class ShortcutsController implements ReactiveController {
+    private host: ReactiveControllerHost;
+    private unsubscribe?: () => void;
+
+    constructor(host: ReactiveControllerHost) {
+        this.host = host;
+        host.addController(this);
+    }
+
+    // ===================================================================
+    // LIFECYCLE HOOKS
+    // ===================================================================
+
+    hostConnected(): void {
+        this.unsubscribe = shortcutsStore.subscribe(() => {
+            this.host.requestUpdate();
+        });
+    }
+
+    hostDisconnected(): void {
+        this.unsubscribe?.();
+    }
+
+    // ===================================================================
+    // STATE ACCESSORS
+    // ===================================================================
+
+    get state(): Readonly<ShortcutsState> {
+        return shortcutsStore.getState();
+    }
+
+    get bindings(): Map<string, string> {
+        return shortcutsStore.getBindings();
+    }
+
+    // ===================================================================
+    // ACTIONS
+    // ===================================================================
+
+    async updateBinding(
+        action: string,
+        key: string,
+    ): Promise<void> {
+        await shortcutsStore.updateBinding(action, key);
+    }
+
+    async resetAll(): Promise<void> {
+        await shortcutsStore.resetAll();
+    }
+}