Add social quick login and user sync API

Add quick provider login buttons (Auth0 connections), an API to upsert users into Postgres and gate admin via can_manage, plus schema and Node server.

Co-authored-by: Cursor <cursoragent@cursor.com>

db/schema.sql

@@ -0,0 +1,27 @@
+-- NCUE user table for admin gating / auditing
+-- Run: psql -h $DB_HOST -p $DB_PORT -U $DB_USER -d $DB_NAME -f db/schema.sql
+
+DO $$
+BEGIN
+  IF NOT EXISTS (
+    SELECT 1
+    FROM information_schema.tables
+    WHERE table_schema = 'public'
+      AND table_name = 'ncue_user'
+  ) THEN
+    CREATE TABLE public.ncue_user (
+      sub            text PRIMARY KEY,
+      email          text,
+      name           text,
+      picture        text,
+      provider       text,
+      last_login_at  timestamptz,
+      can_manage     boolean NOT NULL DEFAULT false,
+      created_at     timestamptz NOT NULL DEFAULT now(),
+      updated_at     timestamptz NOT NULL DEFAULT now()
+    );
+
+    CREATE INDEX idx_ncue_user_email ON public.ncue_user (email);
+  END IF;
+END $$;
+