[P1] Audit: Favorites and recent tools are missing

[baixiangcpp]

Imported from the byteflow.tools deep audit on 2026-06-22.

Problem: the site contains 123 tools, but there is no obvious way for returning users to pin favorites or jump back to recently used tools. This makes repeat usage slower and reduces retention.

Affected components:

• Header navigation
• Home page
• All Tools page
• Tool cards
• Local storage preference model

Reproduction steps:

1. Use several tools such as JSON Formatter, JWT Decoder, Hash Generator, and Image Resizer.
2. Return to the home page or All Tools page.
3. Look for a recent tools list, pinned tools, or favorites section.
4. Reload the browser and check whether previously used tools are easy to access.

Expected behavior: users should be able to mark tools as favorites and see recent tools, stored locally only with clear privacy copy.

Actual behavior: tool discovery starts from search/category each time. There is no visible favorites or recent tools feature.

Impact: repeat workflows are slower, power users have less reason to install the PWA, and product stickiness is weaker.

Proposed fix:

• Add a local-only Favorites feature on tool cards and tool pages.
• Add a Recent Tools section on home, All Tools, and command palette.
• Store only tool IDs and timestamps locally, not input/output.
• Add controls to clear recent tools and remove favorites.
• Include a privacy note explaining that no payloads are stored.

Acceptance criteria:

• Users can favorite/unfavorite tools.
• Recently used tools appear after visiting tools.
• Stored data contains only tool IDs and timestamps.
• Users can clear recent history.
• Feature works offline after app assets are cached.

[baixiangcpp]

Closed as completed by the canonical BF audit backlog work. This older non-BF audit issue duplicates work now merged through PRs #209-#219, with the BF issues closed and guard/test coverage in place. The remaining non-duplicate follow-up is #7, which stays open because the upstream Next/PostCSS advisory is not fixed yet.