feat(onboarding): add settings.onboarding column + markOnboardingDoneAction

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/db/schema/01_setting.ts

@@ -20,6 +20,7 @@ export const setting = pgTable("settings", {
     defaultStorageChannelId: uuid('default_storage_channel_id')
         .references(() => storageChannel.id, {onDelete: "set null"}),
     encryption: boolean("encryption").default(false),
+    onboarding: boolean("onboarding").default(false).notNull(),
     ...timestamps
 });