feat(backend): add DB persistence layer (#79)

* feat(backend): add DB persistence layer

Replace raw pg Pool with Drizzle ORM backed by Bun.sql.
Add per-user source configuration table (user_sources).
Migrate Better Auth to drizzle-adapter.
Add AES-256-GCM credential encryption.

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

* fix(backend): set updatedAt explicitly in all mutations

onConflictDoUpdate bypasses Drizzle's $onUpdate hook.
Set updatedAt explicitly in all mutation methods.

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

* fix(backend): add composite index on user_sources

Add (user_id, enabled) index for the enabled() query path.

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

---------

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

apps/aelis-backend/src/lib/crypto.test.ts

@@ -0,0 +1,62 @@
+import { randomBytes } from "node:crypto"
+import { describe, expect, test } from "bun:test"
+
+import { CredentialEncryptor } from "./crypto.ts"
+
+const TEST_KEY = randomBytes(32).toString("base64")
+
+describe("CredentialEncryptor", () => {
+	const encryptor = new CredentialEncryptor(TEST_KEY)
+
+	test("round-trip with simple string", () => {
+		const plaintext = "hello world"
+		const encrypted = encryptor.encrypt(plaintext)
+		expect(encryptor.decrypt(encrypted)).toBe(plaintext)
+	})
+
+	test("round-trip with JSON credentials", () => {
+		const credentials = JSON.stringify({
+			accessToken: "ya29.a0AfH6SMB...",
+			refreshToken: "1//0dx...",
+			expiresAt: "2025-12-01T00:00:00Z",
+		})
+		const encrypted = encryptor.encrypt(credentials)
+		expect(encryptor.decrypt(encrypted)).toBe(credentials)
+	})
+
+	test("round-trip with empty string", () => {
+		const encrypted = encryptor.encrypt("")
+		expect(encryptor.decrypt(encrypted)).toBe("")
+	})
+
+	test("round-trip with unicode", () => {
+		const plaintext = "日本語テスト 🔐"
+		const encrypted = encryptor.encrypt(plaintext)
+		expect(encryptor.decrypt(encrypted)).toBe(plaintext)
+	})
+
+	test("each encryption produces different ciphertext (unique IV)", () => {
+		const plaintext = "same input"
+		const a = encryptor.encrypt(plaintext)
+		const b = encryptor.encrypt(plaintext)
+		expect(a).not.toEqual(b)
+		expect(encryptor.decrypt(a)).toBe(plaintext)
+		expect(encryptor.decrypt(b)).toBe(plaintext)
+	})
+
+	test("tampered ciphertext throws", () => {
+		const encrypted = encryptor.encrypt("secret")
+		encrypted[13]! ^= 0xff
+		expect(() => encryptor.decrypt(encrypted)).toThrow()
+	})
+
+	test("truncated data throws", () => {
+		expect(() => encryptor.decrypt(Buffer.alloc(10))).toThrow("Encrypted data is too short")
+	})
+
+	test("throws when key is wrong length", () => {
+		expect(() => new CredentialEncryptor(Buffer.from("too-short").toString("base64"))).toThrow(
+			"must be 32 bytes",
+		)
+	})
+})

apps/aelis-backend/src/lib/crypto.ts

@@ -0,0 +1,60 @@
+import { createCipheriv, createDecipheriv, randomBytes } from "node:crypto"
+
+const ALGORITHM = "aes-256-gcm"
+const IV_LENGTH = 12
+const AUTH_TAG_LENGTH = 16
+
+/**
+ * AES-256-GCM encryption for credential storage.
+ *
+ * Caches the parsed key on construction to avoid repeated
+ * env reads and Buffer allocations.
+ */
+export class CredentialEncryptor {
+	private readonly key: Buffer
+
+	constructor(base64Key: string) {
+		const key = Buffer.from(base64Key, "base64")
+		if (key.length !== 32) {
+			throw new Error(
+				`Encryption key must be 32 bytes (got ${key.length}). Generate with: openssl rand -base64 32`,
+			)
+		}
+		this.key = key
+	}
+
+	/**
+	 * Encrypts plaintext using AES-256-GCM.
+	 *
+	 * Output format: [12-byte IV][ciphertext][16-byte auth tag]
+	 */
+	encrypt(plaintext: string): Buffer {
+		const iv = randomBytes(IV_LENGTH)
+		const cipher = createCipheriv(ALGORITHM, this.key, iv)
+
+		const encrypted = Buffer.concat([cipher.update(plaintext, "utf8"), cipher.final()])
+		const authTag = cipher.getAuthTag()
+
+		return Buffer.concat([iv, encrypted, authTag])
+	}
+
+	/**
+	 * Decrypts a buffer produced by `encrypt`.
+	 *
+	 * Expects format: [12-byte IV][ciphertext][16-byte auth tag]
+	 */
+	decrypt(data: Buffer): string {
+		if (data.length < IV_LENGTH + AUTH_TAG_LENGTH) {
+			throw new Error("Encrypted data is too short")
+		}
+
+		const iv = data.subarray(0, IV_LENGTH)
+		const authTag = data.subarray(data.length - AUTH_TAG_LENGTH)
+		const ciphertext = data.subarray(IV_LENGTH, data.length - AUTH_TAG_LENGTH)
+
+		const decipher = createDecipheriv(ALGORITHM, this.key, iv)
+		decipher.setAuthTag(authTag)
+
+		return Buffer.concat([decipher.update(ciphertext), decipher.final()]).toString("utf8")
+	}
+}