feat(mvp): phase 8 - integration, testing & deployment

Fix all build/type/lint errors (zod 3.25 compat wrapper, Svelte 5 fixes),
write 115 unit tests across 10 test files, expand seed script with demo
data, update Docker config with migration on startup.

src/routes/admin/settings/+page.server.ts

@@ -1,6 +1,6 @@
 import type { Actions, PageServerLoad } from './$types.js';
 import { superValidate, setError } from 'sveltekit-superforms';
-import { zod } from 'sveltekit-superforms/adapters';
+import { zod } from '$lib/utils/zod-adapter.js';
 import { fail } from '@sveltejs/kit';
 import { requireAdmin } from '$lib/server/middleware/authorize.js';
 import { prisma } from '$lib/server/prisma.js';