[codex] add Appwrite, Supabase, Hoppscotch, and Excalidraw

[Sean-Kenneth-Doherty]

Summary

• Adds Appwrite, Supabase, Hoppscotch, and Excalidraw to the project list.
• Includes each project's GitHub avatar, contribution link, concise tags, and live beginner issue loading.
• Contributes to Add projects to project list #1.

Why

These are active, unarchived repositories with open good first issue items, giving first-time contributors more current places to start.

Validation

• pnpm build
• git diff --check
• Verified each of the four projects appears exactly once in src/data/projects.js with the expected /contribute URL.
• Verified all four /contribute pages return HTTP 200 and all four avatar URLs return image content.

[Sean-Kenneth-Doherty]

Moved out of draft after local validation:

• pnpm build
• git diff --check
• Source scan confirmed exactly one Appwrite card and one Hoppscotch card at the time this PR was moved ready, with the expected contribute URLs.
• Live URL checks returned HTTP 200 for both contribute pages and image content for both GitHub avatar URLs.

Follow-up commit c57ee5f later added Supabase and Excalidraw as well; the PR body now reflects the current four-project validation.

[Sean-Kenneth-Doherty]

Withdrawing to reduce review noise from the large batch of small project-list PRs. I am keeping the more concrete bug/security/accessibility fixes open instead.