feat: Netlify deployment support

[Copilot]

Switches from adapter-auto to @sveltejs/adapter-netlify and adds the configuration Netlify needs to build and serve the app.

Changes

• svelte.config.js — Replace @sveltejs/adapter-auto with @sveltejs/adapter-netlify
• netlify.toml (new) — Defines build command, publish directory (build), Node 20, and documents all required/optional env vars
  • Build command is npm run compile:contracts && npm run build because the /deploy route statically imports Hardhat-compiled contract artifacts that are .gitignored and must be generated at build time
• .gitignore — Add build/ and .netlify/ (adapter output dirs)
• .prettierignore — Add .netlify/ to suppress linter noise on generated files

[build]
  command = "npm run compile:contracts && npm run build"
  publish = "build"

[build.environment]
  NODE_VERSION = "20"

Server-side routes (src/routes/api/) are automatically handled via Netlify Functions by the adapter — no manual [[redirects]] configuration needed.

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[netlify]

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