Translate the labels the extractor could not see

Three places built user-visible English out of expressions rather than
writing it as JSX text, so the extraction codemod never found them and
they stayed English in all nine languages — including the five that have
been in production for weeks.

The calendar view switcher was the worst of them: it spelled its labels
as `v[0].toUpperCase() + v.slice(1)`, which is correct English and
untranslatable anywhere else. Day, Week, Month and Agenda were already in
every catalogue, sitting unused, because the buttons never asked for
them. They now come from a Record<View, () => string>, so TypeScript
makes the map exhaustive and adding a view forces adding its label. The
labels are functions rather than values: a module-level object would
capture whichever language happened to load first and keep it.

The other two needed new source strings, added to all nine catalogues:
the composer's title for an untitled draft ("New message"), its status
line ("Sending…", "Saving…", "Error", "Saved {when}", "Unsaved"), and the
agenda view's own title ("Agenda from {date}").

This is not the whole of it. A sweep for the same shape — template
literals, toast arguments, and dialog props rather than JSX text — turns
up roughly a hundred more strings, mostly toasts and confirmation
dialogs. Those are a second extraction pass rather than a fix, and are
left for one.

web/src/locales/nl.ts

@@ -844,6 +844,15 @@ export const catalog: Catalog = {
     "This translation was generated by AI and has not been checked by a native speaker, so it is marked Beta until somebody who speaks it signs it off. Anything that reads wrongly is worth reporting — {report}.": "Deze vertaling is door AI gemaakt en niet gecontroleerd door iemand met Nederlands als moedertaal; ze is daarom als Beta gemarkeerd tot iemand haar goedkeurt. Alles wat verkeerd klinkt, is een melding waard — {report}.",
     "{name} is the palette from {site}, and what a new account starts on. It is a dark theme, so it counts as dark wherever that matters, and the accent colour below still applies on top of it.": "{name} is het kleurenpalet van {site}, en waarmee een nieuw account begint. Het is een donker thema en telt dus overal als donker waar dat uitmaakt; de accentkleur hieronder werkt er nog steeds bovenop.",
     "ihasmail's own version is the date of the commit it was built from, followed by where that commit came from: {example} was built from a commit dated the 30th of August 2026 that arrived through pull request 129. A commit that did not come through one carries its short SHA instead — {sha}. The version deliberately says nothing about Stalwart; what this build needs from the server is the line above.": "De eigen versie van ihasmail is de datum van de commit waaruit het is gebouwd, gevolgd door waar die commit vandaan kwam: {example} is gebouwd uit een commit van 30 augustus 2026 die via pull request 129 binnenkwam. Een commit die niet via zo'n verzoek kwam, draagt in plaats daarvan zijn korte SHA — {sha}. De versie zegt bewust niets over Stalwart; wat deze build van de server nodig heeft, staat op de regel hierboven.",
+
+    // ── Composer status, calendar title ────────────────────────────────
+    "New message": "Nieuw bericht",
+    "Sending…": "Bezig met verzenden…",
+    "Saving…": "Bezig met opslaan…",
+    "Error": "Fout",
+    "Saved {when}": "Opgeslagen {when}",
+    "Unsaved": "Niet opgeslagen",
+    "Agenda from {date}": "Agenda vanaf {date}",
   },
   plurals: {
     "{n} messages": { one: "{n} bericht", other: "{n} berichten" },