feat: initial HELIX scaffold — R&D showcase platform

SvelteKit 2 + Svelte 5 + TypeScript site. SQLite via Drizzle. Gitea OAuth
for authoring (RnD org-gated). Pure SVG + CSS DNA helix on landing.

What lands
- Landing hero with animated two-strand SVG helix + tagline
- /projects + /projects/[slug] (markdown body, dashboard embed allowlist)
- /posts + /posts/[slug]
- Auth-gated /projects/new + /posts/new forms
- Gitea OAuth flow (state, code exchange, org-membership check, sessions)
- Sliding-window cookie sessions (SHA-256 hashed token storage)
- Dockerfile + docker-compose with named-volume SQLite
- Idempotent seed (EVOLV + HELIX projects, welcome post)

Stack notes
- Tailwind v3 (Node 18 compat; v4 needs Node 20+)
- drizzle-orm 0.45+ (patched, no SQL-identifier escape vuln)
- marked for markdown; iframe embeds gated by DASHBOARD_ALLOWED_HOSTS

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/routes/+layout.server.ts

@@ -0,0 +1,5 @@
+import type { LayoutServerLoad } from './$types';
+
+export const load: LayoutServerLoad = async ({ locals }) => ({
+  user: locals.user
+});