Add Dia browser support on macOS

[YNDmitry]

Summary

Adds support for the Dia browser on macOS.

Dia stores cookies in a Chromium-style profile under:

~/Library/Application Support/Dia/User Data

but uses its own macOS keychain entry:

• account: Dia
• service/name: Dia Safe Storage

This PR adds:

• a new browser/dia package
• automatic Dia finder registration through browser/all
• Dia safe storage documentation in internal/chrome/README.md

Verification

Tested with:

go test ./...
GOOS=linux GOARCH=amd64 go test ./browser/dia ./browser/all
GOOS=windows GOARCH=amd64 go test ./browser/dia ./browser/all
go run ./cmd/kooky -b dia -j

The local smoke test successfully detected and decrypted cookies from an installed Dia profile on macOS.

Notes

This change currently adds automatic Dia profile discovery on macOS, which is the platform I was able to verify locally.