Fix SMTP delivery, add password reset and user deletion

SMTP:
- Add connection/greeting/socket timeouts so a stalled Gmail
  connection no longer hangs sign-up
- Wrap sendMail in try/catch and fall back to logging the code
- Derive secure from port (465 implicit TLS vs 587 STARTTLS)
- Strip whitespace from the Gmail app password
- Document SMTP_HOST/SMTP_PORT in .env.example and environment.d.ts

Password reset (new):
- POST /(api)/auth/forgot-password emails a 6-digit code and does
  not reveal whether the address is registered
- POST /(api)/auth/reset-password validates the code, sets the new
  password, verifies the email, and signs the user in
- password_reset_codes table added to seed-db.mjs
- "Forgot password?" flow on the mobile sign-in screen

User deletion (new):
- DELETE /(api)/admin/users/[id], owner-only, blocks self-deletion
- Delete button with confirmation on the dashboard Users page

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

components/oauth.tsx

@@ -14,12 +14,36 @@ type OAuthProps = {
 };
 
 export const OAuth = ({ title }: OAuthProps) => {
+  const clientId = process.env.EXPO_PUBLIC_GOOGLE_AUTH_WEB_CLIENT_ID;
+  const iosClientId = process.env.EXPO_PUBLIC_GOOGLE_AUTH_IOS_CLIENT_ID;
+  const androidClientId =
+    process.env.EXPO_PUBLIC_GOOGLE_AUTH_ANDROID_CLIENT_ID;
+
+  const isConfigured = Boolean(
+    clientId && (androidClientId || iosClientId),
+  );
+
+  if (!isConfigured) return null;
+
+  return <GoogleOAuth title={title} clientId={clientId!} iosClientId={iosClientId} androidClientId={androidClientId} />;
+};
+
+function GoogleOAuth({
+  title,
+  clientId,
+  iosClientId,
+  androidClientId,
+}: OAuthProps & {
+  clientId: string;
+  iosClientId?: string;
+  androidClientId?: string;
+}) {
   const { setSession } = useSession();
 
   const [request, response, promptAsync] = Google.useIdTokenAuthRequest({
-    clientId: process.env.EXPO_PUBLIC_GOOGLE_AUTH_WEB_CLIENT_ID,
-    iosClientId: process.env.EXPO_PUBLIC_GOOGLE_AUTH_IOS_CLIENT_ID,
-    androidClientId: process.env.EXPO_PUBLIC_GOOGLE_AUTH_ANDROID_CLIENT_ID,
+    clientId,
+    iosClientId,
+    androidClientId,
   });
 
   useEffect(() => {
@@ -78,4 +102,4 @@ export const OAuth = ({ title }: OAuthProps) => {
       />
     </View>
   );
-};
+}