Wire cljs frontend to the backend with session login

- frontend: hash routing (project list / create / editor), per-project init
  (load OTIO + scene + clip from the API), create form with otio + clip upload,
  annotation saves/deletes pushed as deltas, edit/add buttons gated on auth
- auth: own login form in cljs posting to session login/logout endpoints
  (httpOnly cookie — no JWT in JS); /api/me/ drives the UI's signed-in state
- backend: add /api/login/ and /api/logout/ (session auth)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scenes/views.py

@@ -1,5 +1,6 @@
 import json
 
+from django.contrib.auth import authenticate, login as dj_login, logout as dj_logout
 from django.db.models import Q
 from django.http import HttpResponseNotAllowed, JsonResponse
 from django.shortcuts import get_object_or_404
@@ -42,11 +43,34 @@ def _meta(request, project):
     }
 
 
+def _who(user):
+    return {"authenticated": user.is_authenticated,
+            "username": user.get_username() if user.is_authenticated else None}
+
+
 def me(request):
     """GET /api/me/ — who the browser is logged in as (for the UI to gate edits)."""
-    u = request.user
-    return JsonResponse({"authenticated": u.is_authenticated,
-                         "username": u.get_username() if u.is_authenticated else None})
+    return JsonResponse(_who(request.user))
+
+
+@csrf_exempt
+def login_view(request):
+    """POST /api/login/ {username, password} — start a session (httpOnly cookie)."""
+    if request.method != "POST":
+        return HttpResponseNotAllowed(["POST"])
+    data = json.loads(request.body or "{}")
+    user = authenticate(request, username=data.get("username"), password=data.get("password"))
+    if user is None:
+        return JsonResponse({"detail": "invalid username or password"}, status=400)
+    dj_login(request, user)
+    return JsonResponse(_who(user))
+
+
+@csrf_exempt
+def logout_view(request):
+    """POST /api/logout/ — end the session."""
+    dj_logout(request)
+    return JsonResponse(_who(request.user))
 
 
 @csrf_exempt