Missing NOTIFICATIONS.md reference in MiniKit to Farcaster migration mapping

## Summary

[skills/converting-minikit-to-farcaster/MAPPING.md](cci:7://file:///C:/Users/Zeki/CascadeProjects/skills-research/skills/converting-minikit-to-farcaster/MAPPING.md:0:0-0:0) references `NOTIFICATIONS.md`, but that file does not appear to exist in the skill directory.

## What I found

The missing reference appears in two places:

- `skills/converting-minikit-to-farcaster/MAPPING.md:412`
- `skills/converting-minikit-to-farcaster/MAPPING.md:452`

Current text:

`See [NOTIFICATIONS.md](NOTIFICATIONS.md) for server-side implementation.`

However, there is no `NOTIFICATIONS.md` file under:

`skills/converting-minikit-to-farcaster/`

## Expected behavior

The notification migration section should either:

- Link to an existing documentation file, or
- Include a new `NOTIFICATIONS.md` file with the referenced server-side notification guidance.

## Suggested fix

Add `skills/converting-minikit-to-farcaster/NOTIFICATIONS.md` or update the links to point to the correct existing reference.

## Impact

Users following the MiniKit to Farcaster migration skill may hit a broken local reference when migrating notification functionality.

Start by inspecting skills/converting-minikit-to-farcaster/MAPPING.md at lines 412 and 452, then check the skill directory for an existing notification reference. Confirm whether the links should target an existing document or a new NOTIFICATIONS.md file. Done means the notification migration section has a valid local reference and no broken link.

Written by the indexing model from the issue text.