Fix macOS build failures and missing dependencies in setup.sh

### Description

The current `setup.sh` script fails or produces incorrect builds on modern macOS (Apple Silicon arm64) for a few reasons:

1. **Incorrect Qt Path:** `aqtinstall` for Qt 6.8.3 on macOS installs the kit into the `macos` directory, but the setup script expects it in `clang_64`. This causes `Qt6Config.cmake` to not be found.
2. **Missing Dependencies:** `yt-dlp` is missing but is required by the project. Additionally, the system might link against x86_64 OpenSSL libraries because `openssl@3` is not explicitly installed and passed to CMake.
3. **OpenSSL Architecture Mismatch:** On Apple Silicon, we must explicitly pass `OPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl@3` to CMake so it finds the correct arm64 libraries instead of mistakenly picking up incompatible ones.

### Proposed Fixes

- Update `QT_KIT` to `"macos"` for Darwin in `setup.sh`.
- Add `openssl@3` and `yt-dlp` to the Homebrew `brew install` list.
- Pass `-DOPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl@3` to CMake if the directory exists.

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