admin dashboard login api (#184)

* auth_login_post stub

* add cognito to cdk

* get cognito values from env

* login mvp

Author: Logan-Dang

app/backend/.env.template

@@ -1,2 +1,3 @@
 TABLE_NAME=
-IMAGE_BUCKET_NAME=
+COGNITO_USER_POOL_ID=
+COGNITO_CLIENT_ID=

app/backend/Cargo.lock

@@ -7,9 +7,11 @@ edition = "2024"
 anyhow = "1.0.102"
 async-trait = "0.1"
 aws-config = { version = "1.8.12", features = ["behavior-version-latest"] }
+aws-sdk-cognitoidentityprovider = "1.110.0"
 aws-sdk-dynamodb = "1.101.0"
 axum = "0.8.8"
 axum-extra = { version = "0.12", features = ["cookie", "query"] }
+dotenvy = "0.15.7"
 http = "1"
 openapi = { path = "./openapi" }
 tokio = { version = "1.48.0", features = ["full"] }