Translate the eight strings that were still falling back

Every catalogue was at 1,255 of 1,279 with 24 strings rendering English.
Eight of those are real UI text and are now translated in all nine
languages: the five sort options that had no entry while their opposites
did (Read first beside Unread first, Unstarred first beside Starred
first, Smallest first beside Largest first, and the two alphabetical
directions), and the three sentences behind the link and external-sender
warnings. Each follows the phrasing its own catalogue already used for
the sibling it sits next to.

The remaining sixteen are left in English deliberately, because
translating them would be wrong: product and project names, the sample
addresses in placeholder text, bare URL prefixes, the ellipsis used as a
masked value, and two mail header names.

Per locale: 1,263 of 1,279, up from 1,255.

**The stale list is not touched, and should not be cleaned blindly.** The
checker reports 41 keys as translated-but-never-looked-up, and some of
them are live. "Classic" is the clearest: the palette picker renders it
through translate(p.name) from a constant, so the extractor sees no
literal, while the German "Klassisch" it would delete is the exact fix
issue #247 asked for. "Add star" and "Remove star" are the same shape,
reached through a ternary in a JSX label. Teaching the extractor those
two call sites is the prerequisite for trusting that list.

web/src/locales/ja.ts

@@ -1220,6 +1220,14 @@ export const catalog: Catalog = {
     "Throw away your changes?": "変更を破棄しますか？",
     "Today, in your date format": "今日（お使いの日付形式）",
     "Unread first": "未読を先頭に",
+    "Read first": "既読を先頭に",
+    "Unstarred first": "スターなしを先頭に",
+    "Smallest first": "サイズの小さい順",
+    "Z to A": "Z→A の順",
+    "A to Z": "A→Z の順",
+    "It reads {shown} but goes to {actual}.": "表示は {shown} ですが、実際のリンク先は {actual} です。",
+    "The full address is {href}.": "完全なアドレスは {href} です。",
+    "This message came from {domain}, which is outside your organisation.": "このメッセージは組織外の {domain} から届いています。",
     "Unsaved changes": "保存されていない変更",
     "View as": "表示形式",
     "Warnings": "警告",