refactor(frontend): Formまわりの型強化 (#16260)

* refactor(frontend): Formまわりの型強化

* fix

* avoid non-null assertion and add null check for safety

* refactor

* avoid non-null assertion and add null check for safety

* Update clip.vue

---------

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

packages/frontend/src/widgets/WidgetUnixClock.vue

@@ -19,29 +19,29 @@ SPDX-License-Identifier: AGPL-3.0-only
 import { onUnmounted, ref, watch } from 'vue';
 import { useWidgetPropsManager } from './widget.js';
 import type { WidgetComponentEmits, WidgetComponentExpose, WidgetComponentProps } from './widget.js';
-import type { GetFormResultType } from '@/utility/form.js';
+import type { FormWithDefault, GetFormResultType } from '@/utility/form.js';
 
 const name = 'unixClock';
 
 const widgetPropsDef = {
 	transparent: {
-		type: 'boolean' as const,
+		type: 'boolean',
 		default: false,
 	},
 	fontSize: {
-		type: 'number' as const,
+		type: 'number',
 		default: 1.5,
 		step: 0.1,
 	},
 	showMs: {
-		type: 'boolean' as const,
+		type: 'boolean',
 		default: true,
 	},
 	showLabel: {
-		type: 'boolean' as const,
+		type: 'boolean',
 		default: true,
 	},
-};
+} satisfies FormWithDefault;
 
 type WidgetProps = GetFormResultType<typeof widgetPropsDef>;
 
@@ -54,7 +54,7 @@ const { widgetProps, configure } = useWidgetPropsManager(name,
 	emit,
 );
 
-let intervalId;
+let intervalId: number | null = null;
 const ss = ref('');
 const ms = ref('');
 const showColon = ref(false);
@@ -84,7 +84,10 @@ watch(() => widgetProps.showMs, () => {
 }, { immediate: true });
 
 onUnmounted(() => {
-	window.clearInterval(intervalId);
+	if (intervalId) {
+		window.clearInterval(intervalId);
+		intervalId = null;
+	}
 });
 
 defineExpose<WidgetComponentExpose>({