build: Install uv through brew

[loewenheim]

I'm getting a warning on every devenv sync saying that installing uv through devenv is no longer supported:

❯ devenv sync
[…]
!!! devenv-managed uv is deprecated! run `brew install uv` !!!

So I'm removing that code and adding uv to the brewfile instead.

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[sentry]

Bug: The script unconditionally uninstalls uv but only provides a re-installation path for macOS, breaking the development environment setup for Linux users by leaving uv missing.
_{Severity: HIGH}

Suggested Fix

Provide a cross-platform installation method for uv. This could involve adding a specific installation step for Linux, similar to the previous implementation that downloaded pre-compiled binaries, or using a package manager available on Linux.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: devenv/sync.py#L12

Potential issue: The script unconditionally calls `uv.uninstall(binroot)` on line 12,
removing the `uv` executable from the development environment on all platforms. However,
the subsequent installation of `uv` is handled by `brew bundle`, which is only executed
on macOS due to an `if constants.DARWIN` check. On Linux systems, `uv` is removed but
never re-installed. This causes the script to fail later at a check for the `uv`
executable (`shutil.which("uv")`), resulting in a `SystemExit` with a misleading error
message suggesting the user run `direnv allow`, which will not resolve the issue.