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>

environment.d.ts

@@ -19,11 +19,12 @@ declare global {
       EXPO_PUBLIC_GOOGLE_AUTH_IOS_CLIENT_ID: string;
       EXPO_PUBLIC_GOOGLE_AUTH_ANDROID_CLIENT_ID: string;
 
-      // gmail api
-      GMAIL_CLIENT_ID: string;
-      GMAIL_CLIENT_SECRET: string;
-      GMAIL_REFRESH_TOKEN: string;
-      GMAIL_FROM: string;
+      // gmail smtp
+      SMTP_HOST: string;
+      SMTP_PORT: string;
+      SMTP_USER: string;
+      SMTP_PASS: string;
+      SMTP_FROM: string;
 
       // geoapify api key
       EXPO_PUBLIC_GEOAPIFY_API_KEY: string;