Add curator roles/permissions with Users admin, and fix lineage branch joins.

Staff accounts use admin/curator roles and fine-grained flags; transitions connect source-to-target with color gradients and stream cutout masks so overlaps stay seamless.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/locales/en/home.json

@@ -17,6 +17,7 @@
   "influences": "Influences",
   "tours": "Tours",
   "toursEditor": "Tour editor",
+  "users": "Users",
   "openingTourGallery": "Opening guided tour…",
   "tourEmpty": "This tour has no paintings yet.",
   "tourLoadFailed": "Failed to load the tour.",

client/src/locales/en/users.json

@@ -0,0 +1,37 @@
+{
+  "title": "Users",
+  "back": "← Back",
+  "loadFailed": "Failed to load users",
+  "createTitle": "Create user",
+  "username": "Username",
+  "password": "Password",
+  "role": "Role",
+  "roleAdmin": "Admin",
+  "roleCurator": "Curator",
+  "permissions": "Permissions",
+  "active": "Active",
+  "inactive": "Disabled",
+  "create": "Create",
+  "creating": "Creating…",
+  "save": "Save",
+  "saving": "Saving…",
+  "resetPassword": "Reset password",
+  "newPassword": "New password",
+  "lastLogin": "Last login",
+  "never": "Never",
+  "selectUser": "Select a user to edit",
+  "loading": "Loading…",
+  "perm_images": "Images (fix/upload/debug)",
+  "perm_checkup": "Checkup",
+  "perm_curator_notes": "Curator notes",
+  "perm_translations": "Translations",
+  "perm_influences": "Influences",
+  "perm_tours": "Tours",
+  "perm_users": "Users",
+  "adminAllPerms": "Admins have all permissions automatically.",
+  "deactivate": "Disable account",
+  "activate": "Enable account",
+  "created": "User created",
+  "saved": "Saved",
+  "passwordReset": "Password updated"
+}