feat: Docker, docker-compose, and deployment config (Task 13)

- Dockerfile: two-stage build (builder installs all deps + vite build; runtime copies dist + server)
- docker-compose.yml: 127.0.0.1:3004:8080, named volume for SQLite, env var interpolation
- .env.example: all required environment variables documented
- .dockerignore: exclude node_modules, dist, data, .env from build context
- vite.config.ts: outDir → ../client/dist, /api proxy to :3001 for dev
- .gitignore: remove Docker entries (files should be tracked for deployment)

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

.env.example

@@ -0,0 +1,17 @@
+# MorseQuest Environment Variables
+# Copy to .env and fill in values
+
+PORT=3001
+NODE_ENV=development
+
+# SMTP (for magic link emails)
+SMTP_HOST=mail.keylinkit.net
+SMTP_PORT=587
+SMTP_USER=noreply@morsequest.keylinkit.net
+SMTP_PASS=
+
+# Admin panel password
+ADMIN_PASSWORD=
+
+# App URL (used in magic link emails)
+APP_URL=http://localhost:3001