feat(library): protect Daedalus workspace-scoped libraries from manual deletion

- Add guard in `library_delete` view to block deletion of libraries
  owned by a Daedalus workspace, redirecting with an error message
- Disable the Delete button in `library_detail.html` for workspace-
  scoped libraries and show a warning alert explaining managed ownership
- Add a "Daedalus workspace" badge in both `library_detail.html` and
  `library_list.html` to visually identify workspace-owned libraries

Prevents state desync between Mnemosyne and Daedalus by ensuring
workspace-scoped libraries can only be removed via the Daedalus
workspace DELETE API endpoint.

mnemosyne/library/templates/library/library_detail.html

@@ -10,17 +10,46 @@
 <div class="flex justify-between items-start mb-6">
     <div>
         <h1 class="text-3xl font-bold">{{ library.name }}</h1>
-        <div class="badge badge-primary mt-2">{{ library.library_type }}</div>
+        <div class="flex flex-wrap gap-2 mt-2">
+            <div class="badge badge-primary">{{ library.library_type }}</div>
+            {% if library.workspace_id %}
+            <div class="badge badge-warning gap-1"
+                 title="Workspace {{ library.workspace_id }}">
+                Daedalus workspace
+            </div>
+            {% endif %}
+        </div>
         {% if library.description %}
         <p class="mt-3 opacity-80">{{ library.description }}</p>
         {% endif %}
     </div>
     <div class="flex gap-2">
         <a href="{% url 'library:library-edit' uid=library.uid %}" class="btn btn-sm btn-outline">Edit</a>
+        {% if library.workspace_id %}
+        <button type="button" class="btn btn-sm btn-error btn-outline" disabled
+                title="This library is managed by Daedalus. Delete it from the Daedalus workspace, not here.">
+            Delete
+        </button>
+        {% else %}
         <a href="{% url 'library:library-delete' uid=library.uid %}" class="btn btn-sm btn-error btn-outline">Delete</a>
+        {% endif %}
     </div>
 </div>
 
+{% if library.workspace_id %}
+<div class="alert alert-warning mb-6">
+    <div>
+        <div class="font-semibold">Managed by Daedalus</div>
+        <div class="text-sm opacity-80">
+            This library was created for Daedalus workspace
+            <code class="font-mono">{{ library.workspace_id }}</code>.
+            Items here are owned by the workspace; deleting the workspace in
+            Daedalus will remove this library. Do not delete it manually.
+        </div>
+    </div>
+</div>
+{% endif %}
+
 <!-- Content-Type Configuration -->
 <div class="collapse collapse-arrow bg-base-200 mb-6">
     <input type="checkbox" />

mnemosyne/library/templates/library/library_list.html

@@ -31,7 +31,14 @@
                     {{ lib.name }}
                 </a>
             </h2>
+            <div class="flex flex-wrap gap-1">
                 <div class="badge badge-outline">{{ lib.library_type }}</div>
+                {% if lib.workspace_id %}
+                <div class="badge badge-warning gap-1" title="Managed by Daedalus workspace {{ lib.workspace_id }} — do not delete from Mnemosyne.">
+                    Daedalus workspace
+                </div>
+                {% endif %}
+            </div>
             {% if lib.description %}
             <p class="text-sm opacity-70 mt-2">{{ lib.description|truncatewords:20 }}</p>
             {% endif %}

mnemosyne/library/views.py

@@ -299,6 +299,17 @@ def library_delete(request, uid):
         messages.error(request, f"Library not found: {e}")
         return redirect("library:library-list")
 
+    # Daedalus owns the lifecycle of workspace-scoped libraries — they can
+    # only be deleted via DELETE /library/api/workspaces/{workspace_id}/.
+    # Block the human delete path so a stray click can't desync state.
+    if lib.workspace_id:
+        messages.error(
+            request,
+            f'"{lib.name}" is managed by Daedalus workspace '
+            f"{lib.workspace_id}. Delete it from Daedalus, not here.",
+        )
+        return redirect("library:library-detail", uid=uid)
+
     if request.method == "POST":
         name = lib.name
         lib.delete()