feat(init): add initial project scaffolding and database schema

- Add Dockerfile for multi-stage production build
- Add Drizzle configuration and initial migration for PostgreSQL schema
- Add project configuration files (.prettierrc, .prettierignore, .dockerignore)
- Define core database tables: assets, memberships, site_settings

src/lib/server/site-resolver.ts

@@ -0,0 +1,31 @@
+import { eq } from 'drizzle-orm';
+import { db } from '$lib/server/db';
+import { sites, siteSettings } from '$lib/server/db/schema';
+import type { SiteContext } from '$lib/shared/types';
+
+/**
+ * Load a site by its slug, including its settings.
+ * Throws if no site matches — this is a hard failure because
+ * every deployment MUST have a valid SITE_SLUG.
+ */
+export async function getSiteBySlug(slug: string): Promise<SiteContext> {
+	const [site] = await db.select().from(sites).where(eq(sites.slug, slug)).limit(1);
+
+	if (!site) {
+		throw new Error(
+			`Site not found for slug: "${slug}". Check your SITE_SLUG environment variable. ` +
+				'Run `npm run db:seed` to create the default "local-dev" site, or insert a matching row into the sites table.'
+		);
+	}
+
+	const [settingsRow] = await db
+		.select()
+		.from(siteSettings)
+		.where(eq(siteSettings.siteId, site.id))
+		.limit(1);
+
+	return {
+		site,
+		settings: (settingsRow?.settings as SiteContext['settings']) ?? {}
+	};
+}