feat: add secure auth, admin and postgres persistence

db/migrations/001_auth.sql

@@ -0,0 +1,7 @@
+CREATE EXTENSION IF NOT EXISTS pgcrypto;
+CREATE TABLE users (id uuid PRIMARY KEY DEFAULT gen_random_uuid(), email text UNIQUE NOT NULL, password_hash text NOT NULL, role text NOT NULL DEFAULT 'user' CHECK (role IN ('user','admin')), created_at timestamptz NOT NULL DEFAULT now());
+CREATE TABLE sessions (token_hash text PRIMARY KEY, user_id uuid NOT NULL REFERENCES users(id) ON DELETE CASCADE, csrf_hash text NOT NULL, expires_at timestamptz NOT NULL, created_at timestamptz NOT NULL DEFAULT now());
+CREATE TABLE roast_plans (id uuid PRIMARY KEY DEFAULT gen_random_uuid(), user_id uuid NOT NULL REFERENCES users(id) ON DELETE CASCADE, plan jsonb NOT NULL, created_at timestamptz NOT NULL DEFAULT now(), updated_at timestamptz NOT NULL DEFAULT now());
+CREATE TABLE app_settings (key text PRIMARY KEY, value text NOT NULL);
+INSERT INTO app_settings(key,value) VALUES ('signup_enabled','true');
+CREATE INDEX roast_plans_user_updated ON roast_plans(user_id, updated_at DESC);