refactor: improve code quality (#8751)

* remove unnecessary if

`Array.prototype.some` already returns a boolean so an if to return
true or false is completely unnecessary in this case.

* perf: use count instead of find

When using `count` instead of `findOneBy`, the data is not
unnecessarily loaded.

* remove duplicate null check

The variable is checked for null in the lines above and the function
returns if so. Therefore, it can not be null at this point.

* simplify `getJsonSchema`

Because the assigned value is `null` and the used keys are only
shallow, use of `nestedProperty.set` seems inappropriate. Because the
value is not read, the initial for loop can be replaced by a `for..in`
loop.

Since all keys will be assigned `null`, the condition of the ternary
expression in the nested function will always be true. Therefore the
recursion case will never happen. With this the nested function can be
eliminated.

* remove duplicate condition

The code above already checks `dragging` and returns if it is truthy.
Checking it again later is therefore unnecessary.

To make this more obvious the `return` is removed in favour of using
an if...else construct.

* remove impossible "unknown" time

The `ago` variable will always be a number and all non-negative numbers
are already covered by other cases, the negative case is handled with
`future` so there is no case when `unkown` could be achieved.

packages/client/src/ui/deck/column.vue

@@ -213,14 +213,13 @@ function onDragover(ev) {
 	if (dragging) {
 		// 自分自身にはドロップさせない
 		ev.dataTransfer.dropEffect = 'none';
-		return;
+	} else {
+		const isDeckColumn = ev.dataTransfer.types[0] === _DATA_TRANSFER_DECK_COLUMN_;
+
+		ev.dataTransfer.dropEffect = isDeckColumn ? 'move' : 'none';
+
+		if (isDeckColumn) draghover = true;
 	}
-
-	const isDeckColumn = ev.dataTransfer.types[0] === _DATA_TRANSFER_DECK_COLUMN_;
-
-	ev.dataTransfer.dropEffect = isDeckColumn ? 'move' : 'none';
-
-	if (!dragging && isDeckColumn) draghover = true;
 }
 
 function onDragleave() {