chore: upgrade to Astro 4.2 + other deps

[jbmoelker]

Changes

• Resolves security issues flagged by Dependabot
• Resolves issue on npm run dev caused by Astro cache (node_modules/.astro/):

19:16:05 [@astrojs/cloudflare] There is no `.dev.vars` file in the root directory, if you have encrypted secrets or environmental variables you Cloudflare recommends to put them in this file
19:16:06 [ERROR] [UnhandledRejection] Astro detected an unhandled rejection. Here's the stack trace:
Error: EEXIST: file already exists, mkdir '/Users/.../code/voorhoede/head-start/node_modules/.astro/'
    at mkdirSync (node:fs:1379:3)
    at LocalPagesRuntime.getCF (file:///Users/.../code/voorhoede/head-start/node_modules/@astrojs/cloudflare/dist/utils/local-runtime.js:114:13)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async middleware (file:///Users/.../code/voorhoede/head-start/node_modules/@astrojs/cloudflare/dist/index.js:66:36)
  Hint:
    Make sure your promises all have an `await` or a `.catch()` handler.
  Error reference:
    https://docs.astro.build/en/reference/errors/unhandled-rejection/
  Stack trace:
    at mkdirSync (node:fs:1379:3)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    [...] See full stack trace in the browser, or rerun with --verbose.

Associated issue

• Resolves https://github.com/voorhoede/head-start/security/dependabot/2
• Resolves https://github.com/voorhoede/head-start/security/dependabot/3

How to test

1. Checkout branch.
2. Run npm run dev.
3. Verify everything still works.

Checklist

• [x] I have performed a self-review of my own code
• [x] I have made sure that my PR is easy to review (not too big, includes comments)
• I have made updated relevant documentation files (in project README, docs/, etc)
• I have added a decision log entry if the change affects the architecture or changes a significant technology
• I have notified a reviewer (minor change)

[cloudflare-pages[bot]]

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