Add TypeScript + Express + Postgres backend with Better Auth

Implements the first temetro backend: an Express 5 API on Postgres via
Drizzle ORM, with authentication and multi-tenant clinics powered by
Better Auth.

- Auth: email/password with required email verification, password reset,
  rate limiting, CSRF/trusted-origins, secure cookies, session audit hook.
- Organizations (clinics) with RBAC (owner/admin/member/viewer) and an
  extended `patient` permission set; member invitations by email.
- Org-scoped patient records mirroring the frontend Patient shape, with
  CRUD endpoints gated by permission (read/write/delete).
- Email helper logs links to the console when SMTP is unset (zero-setup
  local dev); Dockerfile + docker-compose (db + backend + frontend) with
  migrations applied on startup and a configurable Postgres host port.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/lib/email.ts

@@ -0,0 +1,49 @@
+import nodemailer from "nodemailer";
+
+import { env } from "../env.js";
+
+type SendArgs = {
+  to: string;
+  subject: string;
+  text: string;
+  html?: string;
+};
+
+// Lazily build a transport. With SMTP_HOST configured we send real mail;
+// otherwise we fall back to logging the message (and any links) to the
+// server console — zero setup for local / open-source development.
+const transport = env.SMTP_HOST
+  ? nodemailer.createTransport({
+      host: env.SMTP_HOST,
+      port: env.SMTP_PORT ?? 587,
+      secure: (env.SMTP_PORT ?? 587) === 465,
+      auth:
+        env.SMTP_USER && env.SMTP_PASS
+          ? { user: env.SMTP_USER, pass: env.SMTP_PASS }
+          : undefined,
+    })
+  : null;
+
+export async function sendEmail({ to, subject, text, html }: SendArgs): Promise<void> {
+  if (!transport) {
+    console.info(
+      [
+        "",
+        "✉️  [email:console] No SMTP configured — printing instead of sending.",
+        `    to:      ${to}`,
+        `    subject: ${subject}`,
+        `    body:    ${text}`,
+        "",
+      ].join("\n"),
+    );
+    return;
+  }
+
+  await transport.sendMail({
+    from: env.SMTP_FROM,
+    to,
+    subject,
+    text,
+    html: html ?? text,
+  });
+}