feat(i18n): complete translations for mature blur threshold setting

Add translations for the new mature_blur_level setting across all
supported languages:
- zh-CN: 成人内容模糊阈值
- zh-TW: 成人內容模糊閾值
- ja: 成人コンテンツぼかし閾値
- ko: 성인 콘텐츠 블러 임계값
- de: Schwelle für Unschärfe bei jugendgefährdenden Inhalten
- fr: Seuil de floutage pour contenu adulte
- es: Umbral de difuminado para contenido adulto
- ru: Порог размытия взрослого контента
- he: סף טשטוש תוכן מבוגרים

Completes TODOs from previous commit.

locales/zh-TW.json

@@ -292,13 +292,13 @@
             "blurNsfwContentHelp": "模糊成熟（NSFW）內容預覽圖片",
             "showOnlySfw": "僅顯示 SFW 結果",
             "showOnlySfwHelp": "瀏覽和搜尋時過濾所有 NSFW 內容",
-            "matureBlurThreshold": "[TODO: Translate] Mature Blur Threshold",
-            "matureBlurThresholdHelp": "[TODO: Translate] Set which rating level starts blur filtering when NSFW blur is enabled.",
+            "matureBlurThreshold": "成人內容模糊閾值",
+            "matureBlurThresholdHelp": "設定當啟用 NSFW 模糊時，從哪個評級級別開始模糊過濾。",
             "matureBlurThresholdOptions": {
-                "pg13": "[TODO: Translate] PG13 and above",
-                "r": "[TODO: Translate] R and above (default)",
-                "x": "[TODO: Translate] X and above",
-                "xxx": "[TODO: Translate] XXX only"
+                "pg13": "PG13 及以上",
+                "r": "R 及以上（預設）",
+                "x": "X 及以上",
+                "xxx": "僅 XXX"
             }
         },
         "videoSettings": {