feat(client): add GiteaClient with auth and pagination (fixes #1)

- GiteaClient with requests.Session and token auth header
- _get_paginated for automatic pagination (limit=50)
- get_repos, get_latest_release (None on 404), get_milestones
- 9 unit tests with mocked requests.Session
- Fix setuptools build backend in pyproject.toml

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_client.py

@@ -0,0 +1,136 @@
+"""Tests for GiteaClient API client."""
+
+from unittest.mock import MagicMock, patch
+
+
+from gitea_dashboard.client import GiteaClient
+
+
+class TestGiteaClientInit:
+    """Test client initialization and auth."""
+
+    def test_auth_header_is_set(self):
+        """Session must carry Authorization header with token prefix."""
+        client = GiteaClient("http://gitea.local:3000", "my-secret-token")
+        assert client.session.headers["Authorization"] == "token my-secret-token"
+
+    def test_base_url_stored(self):
+        """Base URL is stored without trailing slash."""
+        client = GiteaClient("http://gitea.local:3000/", "tok")
+        assert client.base_url == "http://gitea.local:3000"
+
+
+class TestGetPaginated:
+    """Test internal pagination logic."""
+
+    def _make_client(self):
+        return GiteaClient("http://gitea.local:3000", "tok")
+
+    def test_single_page(self):
+        """When response has fewer items than limit, stop after one request."""
+        client = self._make_client()
+        # Return 3 items (< 50 limit) -> single page
+        mock_resp = MagicMock()
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = [{"id": 1}, {"id": 2}, {"id": 3}]
+
+        with patch.object(client.session, "get", return_value=mock_resp) as mock_get:
+            result = client._get_paginated("/api/v1/user/repos")
+
+        assert result == [{"id": 1}, {"id": 2}, {"id": 3}]
+        # Called exactly once (single page)
+        mock_get.assert_called_once()
+
+    def test_two_pages(self):
+        """When first page is full (limit items), fetch second page."""
+        client = self._make_client()
+
+        page1 = [{"id": i} for i in range(50)]  # Exactly limit=50
+        page2 = [{"id": i} for i in range(50, 60)]  # 10 items -> last page
+
+        mock_resp1 = MagicMock()
+        mock_resp1.raise_for_status = MagicMock()
+        mock_resp1.json.return_value = page1
+
+        mock_resp2 = MagicMock()
+        mock_resp2.raise_for_status = MagicMock()
+        mock_resp2.json.return_value = page2
+
+        with patch.object(client.session, "get", side_effect=[mock_resp1, mock_resp2]):
+            result = client._get_paginated("/api/v1/user/repos")
+
+        assert len(result) == 60
+        assert result == page1 + page2
+
+    def test_pagination_params_forwarded(self):
+        """Extra params are merged with pagination params."""
+        client = self._make_client()
+        mock_resp = MagicMock()
+        mock_resp.raise_for_status = MagicMock()
+        mock_resp.json.return_value = []
+
+        with patch.object(client.session, "get", return_value=mock_resp) as mock_get:
+            client._get_paginated("/api/v1/repos/o/r/milestones", params={"state": "open"})
+
+        call_params = mock_get.call_args[1]["params"]
+        assert call_params["state"] == "open"
+        assert call_params["limit"] == 50
+        assert call_params["page"] == 1
+
+
+class TestGetRepos:
+    """Test get_repos method."""
+
+    def test_get_repos_calls_paginated(self):
+        """get_repos delegates to _get_paginated with correct endpoint."""
+        client = GiteaClient("http://gitea.local:3000", "tok")
+        with patch.object(client, "_get_paginated", return_value=[{"id": 1}]) as mock_pag:
+            result = client.get_repos()
+
+        mock_pag.assert_called_once_with("/api/v1/user/repos")
+        assert result == [{"id": 1}]
+
+
+class TestGetLatestRelease:
+    """Test get_latest_release method."""
+
+    def test_returns_release_on_success(self):
+        """Returns release dict when repo has a release."""
+        client = GiteaClient("http://gitea.local:3000", "tok")
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.json.return_value = {"tag_name": "v1.0", "published_at": "2026-01-01"}
+
+        with patch.object(client.session, "get", return_value=mock_resp):
+            result = client.get_latest_release("admin", "my-repo")
+
+        assert result == {"tag_name": "v1.0", "published_at": "2026-01-01"}
+
+    def test_returns_none_on_404(self):
+        """Returns None when repo has no release (404)."""
+        client = GiteaClient("http://gitea.local:3000", "tok")
+        mock_resp = MagicMock()
+        mock_resp.status_code = 404
+
+        with patch.object(client.session, "get", return_value=mock_resp):
+            result = client.get_latest_release("admin", "no-release-repo")
+
+        assert result is None
+
+
+class TestGetMilestones:
+    """Test get_milestones method."""
+
+    def test_get_milestones_calls_paginated_with_state_open(self):
+        """get_milestones delegates to _get_paginated with state=open."""
+        client = GiteaClient("http://gitea.local:3000", "tok")
+        milestones = [{"title": "v2.0", "open_issues": 3, "closed_issues": 2}]
+
+        with patch.object(client, "_get_paginated", return_value=milestones) as mock_pag:
+            result = client.get_milestones("admin", "my-repo")
+
+        mock_pag.assert_called_once_with(
+            "/api/v1/repos/admin/my-repo/milestones",
+            params={"state": "open"},
+        )
+        assert result == milestones