feat(forge): fondation multi-forges — connexions chiffrées, registre, client GitHub (P0/P1)

- Tables forge_connections/users/workspaces (+ membres, projets,
  états, audit) ; migration des anciennes bases avec portées
  (workspace_id, connection_id) par défaut (1, 1).
- Jetons chiffrés Fernet (KANBANTE_MASTER_KEY ou clé générée en
  base), jamais réaffichés.
- ForgeRegistry : connexion héritée créée depuis l'environnement,
  espace Principal, instantanés préfixés par connexion.
- GitHubClient complet (Bearer, pagination Link, étiquettes par
  nom, PATCH archived, branches via git/refs).
- Paramètres surchargeables en base (résolveur config, P3).

tests/test_github_client.py

@@ -0,0 +1,117 @@
+"""GitHubClient (0.24.0, P1): same protocol as GiteaClient,
+GitHub wire shape underneath. Driven through MockTransport."""
+
+import httpx
+import pytest
+
+from app.github_client import GitHubClient
+
+
+def make_client(handler) -> GitHubClient:
+    return GitHubClient(
+        base_url="https://api.github.com",
+        token="ghp_test",
+        cache_ttl=0,
+        transport=httpx.MockTransport(handler),
+    )
+
+
+async def test_auth_header_is_bearer():
+    seen = {}
+
+    def handler(request):
+        seen["auth"] = request.headers.get("authorization")
+        seen["accept"] = request.headers.get("accept")
+        return httpx.Response(200, json={"login": "octocat"})
+
+    client = make_client(handler)
+    user = await client.get_user()
+    assert user["login"] == "octocat"
+    assert seen["auth"] == "Bearer ghp_test"
+    assert "application/vnd.github+json" in seen["accept"]
+
+
+async def test_pagination_follows_link_headers():
+    def handler(request):
+        if "page=2" in str(request.url):
+            return httpx.Response(200, json=[{"full_name": "a/deux"}])
+        return httpx.Response(
+            200,
+            json=[{"full_name": "a/un"}],
+            headers={
+                "Link": '<https://api.github.com/user/repos?page=2>; rel="next"'
+            },
+        )
+
+    client = make_client(handler)
+    repos = await client._fetch_search_repos()
+    assert [r["full_name"] for r in repos] == ["a/un", "a/deux"]
+
+
+async def test_labels_are_addressed_by_name():
+    seen = {}
+
+    def handler(request):
+        if request.method == "GET" and request.url.path.endswith("/labels"):
+            return httpx.Response(
+                200, json=[{"id": 991, "name": "kanban:todo", "color": "3b82f6"}]
+            )
+        if request.method == "POST":
+            seen["body"] = request.content.decode()
+            return httpx.Response(200, json=[])
+        raise AssertionError(request.url)
+
+    client = make_client(handler)
+    label = await client.ensure_label("a", "b", "kanban:todo", "3b82f6")
+    assert label["id"] == "kanban:todo"  # name, not GitHub's numeric id
+    await client.add_issue_label("a", "b", 7, label["id"])
+    assert '"kanban:todo"' in seen["body"]
+
+
+async def test_search_issues_normalizes_repository():
+    def handler(request):
+        assert "is%3Aissue" in str(request.url) or "is:issue" in str(request.url)
+        return httpx.Response(
+            200,
+            json={
+                "items": [
+                    {
+                        "number": 3,
+                        "title": "T",
+                        "repository_url": "https://api.github.com/repos/a/b",
+                    }
+                ]
+            },
+        )
+
+    client = make_client(handler)
+    issues = await client.search_issues(q="mot", state="open")
+    assert issues[0]["repository"]["full_name"] == "a/b"
+
+
+async def test_set_archived_uses_patch():
+    seen = {}
+
+    def handler(request):
+        seen["method"] = request.method
+        seen["body"] = request.content.decode()
+        return httpx.Response(200, json={"archived": True})
+
+    client = make_client(handler)
+    await client.set_archived("a", "b", True)
+    assert seen["method"] == "PATCH"
+    assert '"archived": true' in seen["body"] or '"archived":true' in seen["body"]
+
+
+async def test_starred_roundtrip():
+    seen = {}
+
+    def handler(request):
+        seen["method"] = request.method
+        seen["path"] = request.url.path
+        return httpx.Response(204)
+
+    client = make_client(handler)
+    await client.set_starred("a", "b", True)
+    assert seen["method"] == "PUT"
+    assert seen["path"] == "/user/starred/a/b"