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.

Dockerfile

@@ -37,4 +37,4 @@ EXPOSE 3000
 HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
 	CMD wget -qO- http://localhost:3000/api/health || exit 1
 
-CMD ["node", "build"]
+CMD ["sh", "-c", "npx prisma migrate deploy 2>/dev/null || npx prisma db push --skip-generate && node build"]