Add Husky and lint-staged git hooks

[kentcdodds]

Summary

• add Husky and lint-staged to install Git hooks automatically after bun install
• run staged-file formatting plus lint, typecheck, and build on pre-commit
• run local migrations plus Bun, Playwright, and MCP tests on pre-push
• document the new hook workflow in the setup guide and README

Testing

• git add package.json bun.lock README.md docs/agents/setup.md .husky/pre-commit .husky/pre-push .husky/.gitignore && git commit -m "Add Husky git hook automation"
• bun run hooks:pre-push