Initial implementation: multi-tenant Kanban board (Phase 1)

Complete Phase 1 foundation with working board, column, and card CRUD:
- SvelteKit + TypeScript + Tailwind CSS v4 + adapter-node
- Full Prisma schema with 18 tables (tenants, users, boards, columns, cards, etc.)
- Multi-tenant architecture with hostname-based tenant resolution
- Email/password auth with bcrypt + session cookies
- Board/Column/Card API routes with full CRUD
- Fractional indexing for drag-and-drop ordering
- Board view with svelte-dnd-action for column and card drag-and-drop
- Card modal with inline editing
- Auth pages (login, register)
- Board listing with create form
- RLS policies SQL script for tenant isolation
- Prisma RLS client extensions (forTenant/bypassRLS)
- Permission helpers (canEditBoard, canManageMembers, etc.)
- Socket.IO server setup (dev Vite plugin + production Express server)
- Client-side socket store for real-time updates
- Docker Compose (app + PostgreSQL 16) + multi-stage Dockerfile
- Database seed script (default tenant + admin user)

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

src/lib/server/tenant.ts

@@ -0,0 +1,41 @@
+import { prisma } from './db.js';
+
+const tenantCache = new Map<string, { tenant: TenantInfo; expiresAt: number }>();
+const CACHE_TTL = 60_000; // 1 minute
+
+export interface TenantInfo {
+	id: string;
+	name: string;
+	slug: string;
+}
+
+export async function resolveTenant(hostname: string): Promise<TenantInfo | null> {
+	// Strip port from hostname
+	const host = hostname.split(':')[0];
+
+	// Check cache
+	const cached = tenantCache.get(host);
+	if (cached && cached.expiresAt > Date.now()) {
+		return cached.tenant;
+	}
+
+	const record = await prisma.tenantHostname.findUnique({
+		where: { hostname: host },
+		include: { tenant: true }
+	});
+
+	if (!record) return null;
+
+	const tenant: TenantInfo = {
+		id: record.tenant.id,
+		name: record.tenant.name,
+		slug: record.tenant.slug
+	};
+
+	tenantCache.set(host, { tenant, expiresAt: Date.now() + CACHE_TTL });
+	return tenant;
+}
+
+export function clearTenantCache() {
+	tenantCache.clear();
+}