Add Forgejo edit/refresh sync path for space content (T05)

Keep git as source of truth: deep-link to Forgejo editor, manual refresh to
drop cache, and optional signed push webhook for automatic invalidation.

coulomb_social/apps/spaces/urls.py

@@ -5,5 +5,11 @@ from . import views
 app_name = "spaces"
 
 urlpatterns = [
+    path(
+        "hooks/forgejo/",
+        views.forgejo_content_webhook,
+        name="forgejo_webhook",
+    ),
+    path("<slug:slug>/refresh/", views.space_refresh, name="refresh"),
     path("<slug:slug>/", views.space_detail, name="detail"),
 ]