Add Space metadata model and provisional Forgejo content ADR

Introduce tenant-scoped Space/SpaceMembership with list and detail views.
Document markdown-in-Forgejo as content SoR (ADR-0002). Run migrations on
container start so app.coulomb.social picks up the new tables.

coulomb_social/apps/core/views.py

@@ -2,6 +2,8 @@ from django.contrib.auth.decorators import login_required
 from django.http import HttpRequest, HttpResponse, HttpResponseForbidden, JsonResponse
 from django.shortcuts import redirect, render
 
+from coulomb_social.apps.spaces.services import spaces_for_member
+
 from .principal import build_principal
 
 
@@ -19,8 +21,8 @@ def app_home(request: HttpRequest) -> HttpResponse:
             f"Not authorized to view shell ({principal['authz_reason']})."
         )
 
-    # Spaces list is empty until CSOC-WP-0004-T02; keep the product empty-state.
-    spaces: list[dict] = []
+    member = principal.get("member")
+    spaces = list(spaces_for_member(member))
     return render(
         request,
         "core/app_home.html",