Take Dutch out of Beta with the native speaker's final review

Michael (mbjboon-netizen) sent the final corrections for nl.ts and the Dutch
permission labels and signed the language off, so Nederlands no longer
carries the Beta flag in the picker.

The main catalog changes 52 values, mostly "regels" -> "filterregels" and
"post" -> "e-mail(s)". The permission headings move from compound nouns
("Accountbeheer") to verb phrases ("Accounts beheren"), and the reviewer's
note on that is kept in the file. No keys were added or removed, and every
placeholder is intact.

One entry is kept as it was: "It {damage}, ..." stays "Het {damage}, ...".
{damage} is filled with a verb phrase ("stops in the middle of a line"), so
the added "is" would have doubled the verb.

README, FEATURES, ROADMAP and KNOWN-ISSUES now say Dutch has been reviewed
and the other eight have not.

(cherry picked from commit e30fd73d7dbb1463859efbc4048f680d21d64c56)

web/src/lib/__tests__/languages.test.ts

@@ -32,10 +32,12 @@ describe("resolveUiLanguage", () => {
   it("carries the Beta flag until a person has signed the language off", () => {
     // Not a completeness measure. A catalog can be word-for-word finished
     // and still read like a machine wrote it, which is what this marks.
-    // Every shipped language except English is unreviewed, and stays marked
+    // English is the source and Dutch was signed off by a native speaker in
+    // September 2026. Every other language is unreviewed, and stays marked
     // until a person says otherwise.
+    const reviewed = new Set(["en", "nl"]);
     for (const l of UI_LANGUAGES) {
-      if (l.tag === "en") expect(l.beta).toBeUndefined();
+      if (reviewed.has(l.tag)) expect(l.beta).toBeUndefined();
       else expect(l.beta).toBe(true);
     }
   });