Bazel build system

[Frizi]

Pull Request Description

Created a bazel-based build system, implemented a whole GUI build target within it.

Important Notes

• Running pnpm install will install all necessary dependencies, including Bazel itself.
• The .env file with safe defaults is now committed to the repository, at app/gui. The old version at app/ is no longer used.
• Because the .env file is committed, it does not contain anything sensitive, and developers must create .env.local file at app/gui and overwrite the variables as needed. Ask @Frizi or @vitvakatu for a template file.
• You might need a few additional things on Windows:

1. Developer Mode must be enabled to support creating filesystem symlinks. E.g., using this instruction: https://pureinfotech.com/enable-developer-mode-windows-11/
2. You must create either .bazelrc.local at repository root, or %USERPROFILE%\.bazelrc (consult https://bazel.build/run/bazelrc for more possible locations), containing the following:

# Use different drive letter if needed, but the path must be SHORT
startup --output_base=C:/_bzl
common --disk_cache=C:/_bzl-disk
common --repository_cache=C:/_bzl-repo

3. You need to have bash.exe available in PATH, so either:

• install MSYS2 (https://www.msys2.org/)
• or use bash executable provided with Git by adding the following to your PATH variable: C:\Program Files\Git\bin, if you have it installed.
• or configure Git installation selecting the third option: