feat(backend): add BetterAuth email/password authentication

- Add PostgreSQL connection (src/db.ts)
- Configure BetterAuth with email/password (src/auth/index.ts)
- Add session middleware for route protection (src/auth/session-middleware.ts)
- Add registerAuthHandlers for mounting auth routes (src/auth/http.ts)
- Rename index.ts to server.ts
- Add .env.example with required environment variables

Co-authored-by: Ona <no-reply@ona.com>

apps/aris-backend/src/server.ts

@@ -0,0 +1,14 @@
+import { Hono } from "hono"
+
+import { registerAuthHandlers } from "./auth/http.ts"
+
+const app = new Hono()
+
+app.get("/health", (c) => c.json({ status: "ok" }))
+
+registerAuthHandlers(app)
+
+export default {
+	port: 3000,
+	fetch: app.fetch,
+}