chore(lint): add ESLint v9 flat config + Prettier, format codebase

[jbarson]

and resolve lint errors for #18

[jbarson]

Addressed review comment:

• Removed .eslintrc.cjs from the ignores array in eslint.config.mjs so it gets linted.
• Left .eslintrc.cjs as a comment-only file to avoid no-undef and keep it purely informational.
• Added a targeted override in eslint.config.mjs to disable the Prettier rule for eslint.config.mjs and .eslintrc.cjs (avoids a noisy spacing warning while other rules still apply).

Ran npm run lint locally — zero errors/warnings now.

[Copilot]

Pull Request Overview

This PR adds ESLint v9 flat configuration and Prettier to enforce code style consistency and implements a comprehensive formatting update across the entire codebase. The changes standardize quote usage, apply consistent code formatting, and establish proper linting infrastructure.

• Adds ESLint v9 flat config with TypeScript support and Prettier integration
• Converts all single quotes to double quotes throughout the codebase
• Applies consistent formatting with proper line breaks and spacing

Reviewed Changes

Copilot reviewed 11 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
eslint.config.mjs	New ESLint v9 flat configuration with TypeScript and Prettier rules
.prettierrc.json	Prettier configuration with double quotes and 100-char line width
.eslintrc.cjs	Deprecated legacy ESLint config placeholder
package.json	Added lint and format scripts plus ESLint/Prettier dependencies
vite.config.js	Quote style normalization to double quotes
scripts/systemsList.ts	Multiline object formatting for better readability
scripts/jumpLinks.ts	Quote style conversion from single to double quotes
scripts/app.ts	Quote normalization and multiline formatting improvements
scripts/app.test.ts	Quote style and import formatting updates
index.html	HTML formatting improvements and DOCTYPE normalization
css/style.css	CSS formatting improvements and color code normalization