Format Number of Missed Signatures as Fraction

It would be nice to change the format that missed signatures is displayed in, and/or add context to it. The raw number can be useful in some cases, but there are also plenty of times where the raw number alone doesnt give enough information.

It would be good to instead display that value as a fraction (ex: 20 / 50), so that when looking at it, we know how many possible signatures there were.

在 Flask 的評估檢視和範本中尋找顯示遺漏簽章的位置，然後追蹤目前值的計算方式。當顯示內容同時提供遺漏數量和可能的簽章數量，例如「20 / 50」，且現有的評估檢視仍能正確呈現時，工作即告完成。

由索引模型根據 Issue 內容生成。