Adds initial gitlocal CLI and core functionality

Introduces the `gitlocal` command-line tool for managing nested Git repositories.

Includes the following main commands:
- `convert`: Renames `.git` to `.gitlocal`, allowing a parent repository to ignore the converted child repository. Supports recursive scanning and dry-run options. Tracks converted repositories in a global configuration.
- `revert`: Restores `.gitlocal` to `.git`. Includes an option to revert all tracked repositories.
- `status`: Displays a list of all repositories currently tracked by `gitlocal`, showing their path, conversion time, and original remote/branch.

Establishes internal modules for Git operations, configuration management, and recursive repository scanning.
Adds a comprehensive test suite covering core command logic and utility functions.
Initializes Go module and basic project `.gitignore`.

go.mod

@@ -0,0 +1,13 @@
+module git.membo.co.uk/dtomlinson/gitlocal
+
+go 1.23.3
+
+require (
+	github.com/spf13/cobra v1.10.2
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.9 // indirect
+)