feat(settings): show our versioning, not Apple's marketing string

The row read '1.0.0 (2026081501)'. The first half has said 1.0.0 for every build ever
made here and conveys nothing — nobody maintains it, and it cannot distinguish two
builds. What identifies a build is the date-stamped number OAS assigns and writes into
CFBundleVersion before signing.

So the row now shows exactly that, dotted for reading: 2026.08.15.01. The same string
the install page shows, which is the point — 'is the thing on my phone the thing on the
site?' becomes a question you answer by looking rather than by remembering which link
you tapped.

A build that never went through OAS has no such number. Anything that is not exactly
ten digits is shown verbatim as 'dev (…)' rather than sliced into a fake date.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/settings/SettingsScreen.tsx

@@ -76,6 +76,26 @@ export type SettingsScreenProps = {
  * No tabs. The tabbed variant exists for pages with several named sections to choose between; this
  * one has the app's own section and About, and a row of two pills is chrome rather than navigation.
  */
+/**
+ * Which build this is, in OUR versioning rather than Apple's.
+ *
+ * `1.0.0` is a marketing string nobody maintains — it has said 1.0.0 for every build ever made here and
+ * conveys nothing. What identifies a build is the date-stamped number OAS assigns and writes into
+ * CFBundleVersion before signing, which is also what the install page shows. Showing the same string in
+ * both places is the whole point: it makes "is the thing on my phone the thing on the site?" answerable
+ * by looking, rather than by remembering which link was tapped.
+ *
+ * Dotted for reading, stored undotted — 2026081501 becomes 2026.08.15.01.
+ *
+ * A build that has not been through OAS (a cable install, a Metro run) has no such number, so anything
+ * that is not exactly ten digits is shown verbatim instead of being mangled into a fake date.
+ */
+function buildLabel(): string {
+  const raw = Constants.nativeBuildVersion ?? '';
+  if (!/^\d{10}$/.test(raw)) return raw ? `dev (${raw})` : 'dev';
+  return `${raw.slice(0, 4)}.${raw.slice(4, 6)}.${raw.slice(6, 8)}.${raw.slice(8)}`;
+}
+
 export const SettingsScreen = ({
   title,
   onClose,
@@ -166,7 +186,7 @@ export const SettingsScreen = ({
               */}
               <SettingsRow label="Version">
                 <Text style={{ color: palette.textMuted, fontVariant: ['tabular-nums'] }}>
-                  {`${Constants.expoConfig?.version ?? '1.0.0'} (${Constants.nativeBuildVersion ?? 'dev'})`}
+                  {buildLabel()}
                 </Text>
               </SettingsRow>
               {onShowCredits ? (