Manage public keys, over Stalwart's x:PublicKey registry

A new Settings section, next to Identities & signatures: list, add,
rename and remove the OpenPGP public keys and S/MIME certificates
published on this account. Only public material -- no private key is
stored, requested or sent by any of this.

This is PR #67 revived. That branch was built against 0.16.19, closed
unmerged on 2026-08-26, and shares no ancestry with main after the email
scrub, so it is ported rather than rebased: the four files it added are
carried over, the three it edited are applied by hand, and everything it
claimed was re-probed against the live 0.16.20 on 2026-09-05. The i18n
work is new -- nine catalogues landed on 2026-08-31, after that branch
was written.

What the re-probe confirmed, unchanged from 0.16.19:

  - An ordinary user may read *and* write their own keys, though the
    permissions table lists every sysPublicKey* permission as
    administrative. get and query both answered for a normal account,
    and a malformed create came back invalidProperties naming `key`
    rather than forbidden -- a rejection of the key, not of the person.

  - The server parses the key and says precisely what is wrong. So
    ihasmail does not validate key material; the server's message is
    shown verbatim, as password-policy rejections already are.

  - urn:stalwart:jmap is still absent from the session's top-level
    capabilities and present per-account, so the check that reads all
    three places is still the one that works.

What it added, none of which was known before:

  - A key can parse perfectly and still be refused, with different
    words: a sign-and-certify key with no encryption subkey -- what
    `gpg --quick-generate-key` produces -- gets "Could not find any
    suitable keys in OpenPGP public key". That is the rejection somebody
    exporting from GnuPG will actually meet, and it is not a paste
    error, so collapsing both to "invalid key" would send them back to
    the clipboard for a problem that is in the key.

  - emailAddresses comes back as {} when empty -- an object where a JMAP
    list property should be an array. It type-checks, then throws in
    join() while the list renders. normalize() checked the shape
    already; there is now a test saying why, and the mock answers {} the
    same way, because one that helpfully returned [] would let that
    crash ship.

  - A create answers with the id alone, no createdAt, so adding a key
    reloads rather than believing the response.

  - destroy works and leaves the registry empty. PR #67 shipped that
    path untested -- its live probe was refused before anything was
    created, so there was nothing to destroy.

  - Patching `key` is allowed by the server. The mock still refuses it,
    now deliberately rather than for want of evidence: ihasmail replaces
    a key by adding one and removing the old, which keeps createdAt
    meaning what it says.

x:EncryptionAtRest still does not exist on 0.16.20 -- asking for it is
an unknownMethod. encryptionAtRest is a field on x:AccountSettings, and
its value is a typed object ({"@type":"Disabled"}) rather than the bare
string ROADMAP described. Nothing here writes it.

An empty description is now sent as empty rather than filled in with
"Key". The description is stored on the server, so a default invented in
the client would be whichever language the adder happened to be using;
the list labels a blank one at render time instead.

Verified in a browser against the mock, not only in tests: both
rejections reach the toast in the server's own words with the form still
filled in, a good key renders its card, the kind is labelled from the
armour header, renaming persists, removing asks first and empties the
list, and the whole section reads correctly in German.

web/src/locales/pt-BR.ts

@@ -1307,6 +1307,36 @@ export const catalog: Catalog = {
     "Empty “{name}”?": "Esvaziar “{name}”?",
     "Delete them": "Excluir todos",
     "Nothing was deleted": "Nada foi excluído",
+    // ── Encryption keys, over Stalwart's x:PublicKey registry (#67) ──
+    "Encryption keys": "Chaves de criptografia",
+    "Not available on this server": "Não disponível neste servidor",
+    "Public keys are kept in Stalwart's registry, which this server does not offer. ihasmail needs Stalwart 0.16 or newer for it.": "As chaves públicas ficam no registro do Stalwart, que este servidor não oferece. O ihasmail precisa do Stalwart 0.16 ou mais recente para isso.",
+    "Public keys for this account — what other people encrypt to, and what a signature is checked against. These are public by nature: no private key is stored, requested, or sent by ihasmail.": "Chaves públicas desta conta — o que outras pessoas usam para criptografar, e aquilo com que uma assinatura é conferida. Elas são públicas por natureza: o ihasmail não armazena, não pede e não envia nenhuma chave privada.",
+    "No keys yet": "Ainda não há chaves",
+    "Add an OpenPGP public key or an S/MIME certificate to publish it on this account.": "Adicione uma chave pública OpenPGP ou um certificado S/MIME para publicá-lo nesta conta.",
+    "Key added": "Chave adicionada",
+    "Key removed": "Chave removida",
+    "Remove “{name}”?": "Remover “{name}”?",
+    "this key": "esta chave",
+    "Anyone holding it can still use it — removing it here only stops this account offering it.": "Quem já a tem continua podendo usá-la — removê-la aqui apenas faz esta conta parar de oferecê-la.",
+    "Remove key": "Remover chave",
+    "Key description": "Descrição da chave",
+    "Untitled key": "Chave sem título",
+    "Click to rename": "Clique para renomear",
+    "Expired": "Expirada",
+    "Added": "Adicionada",
+    "Addresses": "Endereços",
+    "No expiry set": "Sem validade definida",
+    "Any address on this account": "Qualquer endereço desta conta",
+    "cryptography\u0004Key": "Chave",
+    "Public key": "Chave pública",
+    "Work key": "Chave do trabalho",
+    "Paste the whole armoured block, headers included. The server checks it and says what is wrong if it cannot read it.": "Cole o bloco blindado inteiro, cabeçalhos incluídos. O servidor confere e diz o que está errado se não conseguir lê-lo.",
+    "Add key": "Adicionar chave",
+    "Add a key": "Adicionar uma chave",
+    "Stalwart stores these keys, and this release does no more than manage them: ihasmail does not yet sign, encrypt, decrypt or verify anything with them. Adding one does not by itself start encrypting your mail.": "O Stalwart guarda essas chaves, e esta versão não faz mais do que gerenciá-las: o ihasmail ainda não assina, criptografa, descriptografa nem verifica nada com elas. Adicionar uma não começa a criptografar seus e-mails por si só.",
+    "Unrecognised": "Não reconhecida",
+    "No account to add a key to.": "Não há conta à qual adicionar uma chave.",
   },
   plurals: {
     // ── Third pass ─────────────────────────────────────────────────────