Migrate frontend to TypeScript with Deno-based tooling (#206)

Compiles assets/*.ts via sensiolabs/typescript-bundle (standalone SWC
binary) and adds Deno for formatting, linting, type-checking, and
tests, keeping the project's no-Node/npm approach intact. Wires all
four into CI, the Justfile, and the pre-commit hook.

assets/controllers/fullscreen_controller.ts

@@ -0,0 +1,51 @@
+import { Controller } from '@hotwired/stimulus';
+
+const STORAGE_KEY = 'tvdt-fullscreen';
+
+export default class extends Controller {
+    connect(): void {
+        document.addEventListener('fullscreenchange', this.onFullscreenChange);
+        this.syncState();
+
+        if (
+            sessionStorage.getItem(STORAGE_KEY) === '1' &&
+            !document.fullscreenElement
+        ) {
+            this.request();
+        }
+    }
+
+    disconnect(): void {
+        document.removeEventListener(
+            'fullscreenchange',
+            this.onFullscreenChange,
+        );
+    }
+
+    toggle(): void {
+        if (document.fullscreenElement) {
+            document.exitFullscreen();
+        } else {
+            this.request();
+        }
+    }
+
+    request(): void {
+        document.documentElement.requestFullscreen().catch(() => {});
+    }
+
+    onFullscreenChange = (): void => {
+        sessionStorage.setItem(
+            STORAGE_KEY,
+            document.fullscreenElement ? '1' : '0',
+        );
+        this.syncState();
+    };
+
+    syncState(): void {
+        document.documentElement.classList.toggle(
+            'is-fullscreen',
+            Boolean(document.fullscreenElement),
+        );
+    }
+}