feat: complete Phase 0 Enterprise IAM

src/db/migrations/postgres/0003_create_user_profiles.sql

@@ -0,0 +1,7 @@
+CREATE TABLE IF NOT EXISTS user_profiles (
+    user_id       TEXT PRIMARY KEY NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    email         TEXT,
+    full_name     TEXT,
+    avatar_url    TEXT,
+    metadata_json TEXT
+);