Add GPL-3.0-or-later license headers to source files

- Updated all relevant source files to include the new license header.
- Changed the default license in the configuration from MIT to GPL-3.0-or-later.

FAQ.md

@@ -1,38 +1,46 @@
 # FAQ
 
 ## What is this project about?
+
 `dcr` is a tool for managing C/C++ projects and their dependencies.
 It is inspired by Cargo, but it is not a direct equivalent of Makefile, CMake, or other classic build systems.
 
 The goal is to provide a simpler and easier-to-configure development workflow.
 
 ## How is the project developed?
+
 The project is written in Rust and is primarily developed by one maintainer, Dexoron.
 
 AI tools are used during development, but they do not write the project end-to-end. Their role is limited to supporting specific tasks (for example, suggestions, wording checks, and translations).
 
 ## Which tools are used for development?
+
 Main development stack:
+
 - `RustRover` 2025 - development IDE.
 - `Codex` (`GPT-5.3-Codex (medium)`) - primary AI tool, integrated via JetBrains AI Chat.
 - `Rust` - main project language.
 - `Cargo` - tool for building, testing, and dependency management in Rust projects.
 
 ## Is the project open source?
+
 Yes, the project is open source.
 You can propose ideas, report issues, and contribute code changes.
 
-The project is distributed under the MIT license (see `LICENSE`).
+The project is distributed under the GPL-3.0 license (see `LICENSE`).
 
 ## How can I contribute?
+
 Thank you for contributing.
 You can:
+
 - help with code;
 - help with translations;
 - help with documentation;
 - suggest an idea or report a bug.
 
 ### If you want to submit changes (code, translation, documentation)
+
 1. Fork the required repository: `dexoron/dcr` (main project) or `dexoron/dcr-site` (project website).
 2. Make your changes following the rules in `CONTRIBUTING.md`.
 3. Push changes to your fork.
@@ -40,6 +48,7 @@ You can:
 5. Wait for review.
 
 ### If you want to report a problem or suggest an idea
+
 1. Open the relevant repository: `dexoron/dcr` or `dexoron/dcr-site`.
 2. Go to the `Issues` tab.
 3. Create an Issue and specify its type (bug, suggestion, question/help).
@@ -47,13 +56,17 @@ You can:
 5. Wait for feedback.
 
 ## How do I install `dcr`?
+
 Available installation methods may vary by project version.
 Recommended path:
+
 - check instructions in `README.md`;
 - if there is no prebuilt package for your platform, build from source using `cargo build --release`.
 
 ## How can I get started quickly?
+
 Minimal workflow:
+
 1. Install `dcr`.
 2. Create a project (or open an existing C/C++ project).
 3. Initialize `dcr` configuration.
@@ -63,21 +76,25 @@ Minimal workflow:
 For detailed commands and examples, see `README.md` and the project documentation.
 
 ## What is the project status?
+
 `dcr` is under active development.
 This means some interfaces and behaviors may change between versions.
 
 Before upgrading, check the changelog and release notes.
 
 ## Which systems does `dcr` support?
+
 `dcr` targets modern C/C++ development environments.
 Actual compatibility depends on the `dcr` version, operating system, and toolchain.
 
 Before starting, check documentation for:
+
 - supported operating systems;
 - supported compilers and linkers;
 - version-specific limitations.
 
 ## How is `dcr` different from Make/CMake?
+
 `dcr` does not aim to be a direct replacement for Make/CMake.
 Its main focus is simplifying project and dependency management with a Cargo-like experience.
 
@@ -85,13 +102,17 @@ If you need low-level, full control over build steps, classic tools may be a bet
 If you want a simpler and more uniform configuration model, `dcr` may be more convenient.
 
 ## Where can I find documentation and examples?
+
 Primary sources:
+
 - `README.md` in the repository;
 - project documentation (see the project website);
 - `Issues` for known problems and discussions.
 
 ## How do I report a bug properly?
+
 To make a bug report easy to reproduce, include:
+
 1. `dcr` version.
 2. OS and compiler/toolchain version.
 3. Steps to reproduce.