feat(backend): update DB layer with tests

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/db/db_dev.go

@@ -16,7 +16,7 @@ var DB *pgxpool.Pool
 func Connect() error {
 	// Connect to Postgres inside Docker network
 	dsn := fmt.Sprintf(
-		"postgres://%s:%s@localhost:5432/%s?sslmode=disable",
+		"postgres://%s:%s@localhost:5432/%s?sslmode=disable&require_auth=scram-sha-256",
 		getEnv("POSTGRES_USER"),
 		getEnv("POSTGRES_PASSWORD"),
 		getEnv("POSTGRES_DB"),