feat: add deployment guide, nginx/systemd configs, switch to adapter-node

- Add docs/DEPLOYMENT.md: step-by-step Proxmox LXC guide (Debian 13,
  PostgreSQL, nginx reverse proxy, systemd services)
- Add nginx/innercontext.conf: proxy /api/ → uvicorn, /mcp/ → uvicorn
  with SSE streaming support, / → SvelteKit Node server
- Add systemd/innercontext.service and innercontext-node.service
- Switch frontend from adapter-auto to adapter-node (required for
  +page.server.ts form actions); install adapter-node 5.5.4
- Update README.md: add frontend, MCP sections; fix /skin-snapshots →
  /skincare; update repo layout
- Replace frontend/README.md generic Svelte template with project docs

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

frontend/svelte.config.js

@@ -1,12 +1,9 @@
-import adapter from '@sveltejs/adapter-auto';
+import adapter from '@sveltejs/adapter-node';
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	kit: {
-		// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
-		// If your environment is not supported, or you settled on a specific environment, switch out the adapter.
-		// See https://svelte.dev/docs/kit/adapters for more information about adapters.
-		adapter: adapter()
+		adapter: adapter({ out: 'build' })
 	}
 };