fix(scripts): align setup-dev.sh with shell script conventions

## Description `setup-dev.sh` uses a non-standard shebang (`#!/bin/bash`), short-form set flags (`set -e`), and doesn't pin the `uv` version. Shell script conventions require `#!/usr/bin/env bash`, `set -euo pipefail`, and version pinning matching `setup-dev.ps1`. ## Files | File | Change |

|------|--------|

| `setup-dev.sh` | Fix shebang, set flags, and pin uv version | ## Acceptance Criteria - [ ] Shebang is `#!/usr/bin/env bash`

• [ ] Flags are `set -euo pipefail`
• [ ] uv version pinned matc