refactor: use value semantics for GitHub and Codeberg clients

- Changed github.NewClient() to return Client instead of *Client
- Changed codeberg.NewClient() to return Client instead of *Client
- Updated sync_handlers.go to handle value semantics properly
- Both clients only contain immutable string fields, making value semantics more appropriate

docs: add comprehensive documentation

- Added doc/ directory with full documentation
- Created architecture overview explaining system design
- Added complete API reference for all packages, types, and functions
- Created configuration guide with examples
- Added usage examples and common workflows
- Created development guide for contributors
- Updated README with links to documentation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/test/test-config.json b/test/test-config.json
new file mode 100644
index 0000000..4e01d92
--- /dev/null
+++ b/test/test-config.json
@@ -0,0 +1,12 @@
+{
+  "organizations": [
+    {
+      "host": "file:///home/paul/git/gitsyncer/test/repos/org1",
+      "name": ""
+    },
+    {
+      "host": "file:///home/paul/git/gitsyncer/test/repos/org2",
+      "name": ""
+    }
+  ]
+}