feat: containerize with Docker Compose + Ollama

Add full Docker setup so the app runs with a single 'docker compose up':

- Dockerfile: multi-stage build (node:22-alpine) for the SvelteKit app
- docker-compose.yml: three services:
  1. ollama: runs Ollama server with persistent volume for models
  2. model-init: one-shot container that pulls the configured model
     after Ollama is healthy, then exits
  3. app: the SvelteKit app, starts only after model-init succeeds
- .env.docker: set OLLAMA_MODEL to control which model is pulled
- .dockerignore: keeps image lean
- Switched adapter-auto to adapter-node (required for Docker/Node hosting)
- Updated README with Docker and local dev instructions

Usage:
  docker compose up              # default: llama3
  OLLAMA_MODEL=gemma2 docker compose up  # any Ollama model

.gitignore

@@ -17,6 +17,7 @@ Thumbs.db
 .env.*
 !.env.example
 !.env.test
+!.env.docker
 
 # Vite
 vite.config.js.timestamp-*