feat: auth/stars API, collections and publish routes, star/author migrations

indexium-backend/migrations/20260909000001_authors.sql

@@ -0,0 +1,6 @@
+CREATE TABLE IF NOT EXISTS authors (
+    github_id BIGINT PRIMARY KEY,
+    login VARCHAR(39) NOT NULL UNIQUE,
+    avatar_url TEXT,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);