feat(v1.2.0): retry API, dernier commit, tri, coloration, export JSON

- client.py: _get_with_retry (max 2 retries, backoff lineaire), get_latest_commit
- collector.py: champ last_commit_date dans RepoData
- display.py: colonne "Dernier commit", _sort_repos (name/issues/release/activity),
  _colorize_milestone_due (rouge/jaune/vert selon echeance)
- cli.py: options --sort/-s et --format/-f (table/json)
- exporter.py: nouveau module, repos_to_dicts + export_json
- 88 tests (35 nouveaux), ruff clean

fixes #8, fixes #7, fixes #10, fixes #9, fixes #6

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

tests/test_exporter.py

@@ -0,0 +1,109 @@
+"""Tests for JSON exporter module."""
+
+import json
+
+from gitea_dashboard.collector import RepoData
+from gitea_dashboard.exporter import export_json, repos_to_dicts
+
+
+def _make_repo(
+    name="my-repo",
+    full_name="admin/my-repo",
+    description="A repo",
+    open_issues=3,
+    is_fork=False,
+    is_archived=False,
+    is_mirror=False,
+    latest_release=None,
+    milestones=None,
+    last_commit_date=None,
+):
+    """Build a RepoData for testing."""
+    return RepoData(
+        name=name,
+        full_name=full_name,
+        description=description,
+        open_issues=open_issues,
+        is_fork=is_fork,
+        is_archived=is_archived,
+        is_mirror=is_mirror,
+        latest_release=latest_release,
+        milestones=milestones if milestones is not None else [],
+        last_commit_date=last_commit_date,
+    )
+
+
+class TestReposToDicts:
+    """Test repos_to_dicts function."""
+
+    def test_basic_conversion(self):
+        """Converts a RepoData to dict with correct values."""
+        repo = _make_repo(name="test-repo", open_issues=5)
+        result = repos_to_dicts([repo])
+
+        assert len(result) == 1
+        assert result[0]["name"] == "test-repo"
+        assert result[0]["open_issues"] == 5
+
+    def test_empty_list(self):
+        """Empty input returns empty list."""
+        assert repos_to_dicts([]) == []
+
+    def test_preserves_all_fields(self):
+        """All RepoData fields are present in the output dict."""
+        repo = _make_repo(
+            name="full",
+            full_name="admin/full",
+            description="desc",
+            open_issues=2,
+            is_fork=True,
+            is_archived=False,
+            is_mirror=True,
+            latest_release={"tag_name": "v1.0", "published_at": "2026-01-01"},
+            milestones=[{"title": "v2.0"}],
+            last_commit_date="2026-03-10T00:00:00Z",
+        )
+        result = repos_to_dicts([repo])
+        d = result[0]
+
+        expected_fields = [
+            "name",
+            "full_name",
+            "description",
+            "open_issues",
+            "is_fork",
+            "is_archived",
+            "is_mirror",
+            "latest_release",
+            "milestones",
+            "last_commit_date",
+        ]
+        for field in expected_fields:
+            assert field in d, f"Missing field: {field}"
+
+
+class TestExportJson:
+    """Test export_json function."""
+
+    def test_valid_json(self):
+        """Output is valid JSON (json.loads does not raise)."""
+        repos = [_make_repo(name="repo-a"), _make_repo(name="repo-b")]
+        output = export_json(repos)
+
+        parsed = json.loads(output)
+        assert isinstance(parsed, list)
+        assert len(parsed) == 2
+
+    def test_indented(self):
+        """JSON output is indented by default."""
+        repos = [_make_repo()]
+        output = export_json(repos)
+
+        # Indented JSON has newlines and spaces
+        assert "\n" in output
+        assert "  " in output
+
+    def test_empty_list(self):
+        """Empty repo list produces '[]'."""
+        output = export_json([])
+        assert json.loads(output) == []