Add HOMEBREW_TAP_GITHUB_TOKEN secret for release cask publishing

The release workflow needs a token that can write to KenanBek/homebrew-dbui — the default GITHUB_TOKEN is repo-scoped and 403'd during v0.9.0 (cask was pushed manually that time).

**Action (owner-only):** create a fine-grained PAT with **Contents: Read and write** on **KenanBek/homebrew-dbui** only, and save it as repo secret `HOMEBREW_TAP_GITHUB_TOKEN` in KenanBek/dbui. The workflow already falls back to GITHUB_TOKEN until then (next release will fail its cask step again if unset).

Open the release workflow and confirm where it falls back to GITHUB_TOKEN for cask publishing. An owner must create a fine-grained token with Contents read and write access to KenanBek/homebrew-dbui, save it as HOMEBREW_TAP_GITHUB_TOKEN in KenanBek/dbui, and verify that the next release cask step succeeds.

Written by the indexing model from the issue text.