feat: manage material visibility and shares

The management save/update body takes is_private, author_user_id and
share_user_ids (absent keeps each; a new material gets the caller as
author), and the managed material shows them. New routes PATCH
/materials/{id}/visibility, PUT /materials/{id}/shares and GET /users,
with the MCP tools bm_manage_set_material_visibility,
bm_manage_set_material_shares and bm_manage_list_users. The /bmadmin
form gets the private switch, the author picker and shared_with.

models/materials/columns.yaml

@@ -4,6 +4,9 @@ columns:
         searchable: true
     type:
         label: jz.bm::lang.materials.type
+    is_private:
+        label: jz.bm::lang.materials.is_private
+        type: switch
     course:
         label: jz.bm::lang.common.course
         relation: course

models/materials/fields.yaml

@@ -28,6 +28,18 @@ fields:
         firstDay: 1
         span: right
         comment: jz.bm::lang.materials.published_at_comment
+    is_private:
+        label: jz.bm::lang.materials.is_private
+        type: switch
+        span: left
+        comment: jz.bm::lang.materials.is_private_comment
+    author:
+        label: jz.bm::lang.materials.author
+        type: relation
+        nameFrom: email
+        span: right
+        emptyOption: jz.bm::lang.common.none
+        comment: jz.bm::lang.materials.author_comment
     source:
         label: jz.bm::lang.common.source
         type: text
@@ -47,6 +59,11 @@ fields:
         label: jz.bm::lang.materials.tags
         type: relation
         nameFrom: name
+    shared_with:
+        label: jz.bm::lang.materials.shared_with
+        type: relation
+        nameFrom: email
+        comment: jz.bm::lang.materials.shared_with_comment
     files:
         label: jz.bm::lang.materials.files
         type: fileupload