feat: redesign OAuth success and error pages

[gnapse]

Summary

Redesigned the OAuth callback pages to match Todoist branding and follow modern UI patterns inspired by steipete/gogcli. The new design features a dark theme with animated background orbs, Todoist logo, success/error badges, and a terminal card showcasing CLI commands.

Changes

• Todoist-like theme: Inspired by Todoist landing page, official Todoist logo SVG with drop shadow and success/error badges
• Success page: Green checkmark badge, macOS-style terminal card with example td commands, 30s countdown timer, GitHub link
• Error page: Red X badge, error message, recovery hint with td auth login command
• Color scheme: Todoist red (#e44332), orange (#ff7043), success green (#34A853)
• Fonts: System font stack (no external requests)

Testing

All tests pass (592 tests). Verified locally (see screenshots below)

Demo

Success

Error

[doist-bot]

This PR introduces a polished and visually appealing redesign for the OAuth success and error pages, bringing them in line with Todoist's branding. The new dark theme, animated background, and clear instructional card create a much-improved user experience during the authentication flow. The implementation has a minor layout issue where page content may become inaccessible on smaller viewports due to a CSS overflow setting.

[scottlovegrove]

I wonder if we could extract the html and images to actual files to be included in the package, rather than having them as strings in code 🤔

[henningmu]

Fancy 💅

[gnapse]

I wonder if we could extract the html and images to actual files to be included in the package, rather than having them as strings in code 🤔

It’s possible but adds friction for little gain. tsc doesn’t copy non-TS files, so you’d need:

• A cp src/lib/oauth-*.html dist/lib/ step in the build script (not cross-platform — breaks on Windows)
• readFileSync(new URL('./oauth-success.html', import.meta.url)) at runtime
• A {{message}} placeholder + .replace() for the error template

The HTML is self-contained, changes rarely, and is ~150 lines each. Keeping it inline means tsc is the only build step. No copy gymnastics, no runtime file resolution, works everywhere.

We can consider it for the future if we find ourselves changing this much.