Version the brand images' URLs, so a new mark reaches returning visitors

The logo, favicons and app icons are served from public/img under fixed
names with a browser cache of hours, and the service worker fetches them
through that cache. After the mark changed on 2026-09-27, returning
visitors kept the old cat until their copies expired, and the favicon
and an installed app's icon hold on longer still.

Every URL that names one now carries ?v=BRAND_V (src/lib/brand.ts,
brandImage()): the header, sign-in, About, the mail empty state, the
notification icons, index.html's favicon links, the manifest's icons
and the service worker's shell and notification icons. Date-stamped,
never a counter, for the sites' ASSET_V reason; the three static files
carry the value written out, and the comment says to keep them in step.

web/src/views/mail/MailView.tsx

@@ -4,7 +4,6 @@ import { DEFAULT_SORT, useMail, type ListQuery } from "@/store/mail";
 import { appliesTo, comparatorsFor } from "@/lib/listSort";
 import type { Comparator } from "@/jmap/types";
 import { useSettings } from "@/store/settings";
-import { withBase } from "@/lib/basePath";
 import { useCompose } from "@/store/compose";
 import { buildFilter, describeFilter, parseQuery } from "@/lib/search";
 import { keyboard } from "@/lib/input/keyboard";
@@ -21,6 +20,7 @@ import { isUnknownMailbox } from "@/lib/mailbox/mailboxRoute";
 import { scheduledMailboxIdFrom, useScheduled } from "@/store/scheduled";
 import { plural, t as translate, tNode } from "@/lib/i18n";
 import { mailboxDisplayName } from "@/lib/mailbox/mailboxName";
+import { brandImage } from "@/lib/brand";
 
 export function MailView({ mailboxId, threadId, search }: { mailboxId?: string; threadId?: string; search?: boolean }) {
   const [, navigate] = useLocation();
@@ -468,7 +468,7 @@ export function MailView({ mailboxId, threadId, search }: { mailboxId?: string;
             <ThreadView key={`${threadId}:${openMessageId ?? ""}`} threadId={threadId} messageId={openMessageId} mailboxId={mailboxId ?? null} onBack={() => openThread(null)} actions={actions} onNavigate={(delta) => { const idx = currentRowIndex; const next = ids[idx + delta]; const t = next ? rowThreadId(next) : undefined; if (t) { setFocusId(next!); openThread(t, settings.conversationMode ? null : next!); } }} hasPrev={currentRowIndex > 0} hasNext={currentRowIndex >= 0 && currentRowIndex < ids.length - 1} />
           ) : (
             <div className="no-thread">
-              <img src={withBase("/img/logo.png")} alt="" />
+              <img src={brandImage("/img/logo.png")} alt="" />
               <div>
                 {list?.total
                   ? settings.conversationMode