fix(stats): 数据速览用完整星期名，脚注时间改逐行对齐

- 「提问最集中在 三 19 点前后」：洞察复用了热力图列头的短标签
  stats.wd.*（一…日 / Mon…），那是为窄列头设计的单字词条，
  进句子就成了「三」。新增 stats.weekday.1..7 完整名（周一 / Monday /
  月曜日），洞察改用该组，stats.wd.* 只留给列头；补测试断言锁住。
- 页脚入口文案「数据」→「统计数据」（四语言同步）。
- 页面脚注四条时间由「基准日 x · 计算于 y」一行改为两列网格逐行排列，
  标签统一带冒号，下面两段说明保持独立段落。

internal/i18n/dict_en.go

@@ -953,7 +953,7 @@ var enDict = map[string]string{
 	"theme.name.new-sakura":       "New Sakura",
 
 	// Site statistics page (/stats): aggregate numbers only
-	"site.footer.stats": "Stats",
+	"site.footer.stats": "Statistics",
 	"stats.title":       "Site statistics",
 	"stats.lead":        "Only aggregate numbers here: how many questions the site receives, how fast they get answered, and when people tend to show up. No individual question, asker identity, or source address is shown.",
 	"stats.unavailable": "Statistics are temporarily unavailable. Please check back later.",
@@ -1014,13 +1014,20 @@ var enDict = map[string]string{
 	"stats.reply.5": "3–7 days",
 	"stats.reply.6": "over 7 days",
 
-	"stats.wd.1": "Mon",
-	"stats.wd.2": "Tue",
-	"stats.wd.3": "Wed",
-	"stats.wd.4": "Thu",
-	"stats.wd.5": "Fri",
-	"stats.wd.6": "Sat",
-	"stats.wd.7": "Sun",
+	"stats.wd.1":      "Mon",
+	"stats.wd.2":      "Tue",
+	"stats.wd.3":      "Wed",
+	"stats.wd.4":      "Thu",
+	"stats.wd.5":      "Fri",
+	"stats.wd.6":      "Sat",
+	"stats.wd.7":      "Sun",
+	"stats.weekday.1": "Monday",
+	"stats.weekday.2": "Tuesday",
+	"stats.weekday.3": "Wednesday",
+	"stats.weekday.4": "Thursday",
+	"stats.weekday.5": "Friday",
+	"stats.weekday.6": "Saturday",
+	"stats.weekday.7": "Sunday",
 
 	"stats.foot.dataDate":   "Data as of",
 	"stats.foot.updated":    "computed at",