fix(learn): the dictionaries' image copies third_party/, as the servers' do

The deploy of 55c73a7e failed building it: the root's dependency
overrides name the three patched plugins by path, and pub refuses a
path that isn't there (exit 66), though the curator uses none of them.
The servers' Dockerfiles got the copy with the overrides; the
curator's was missed. Checked by running each image's steps up to
`dart pub get` in an empty folder: the curator's failed as on the
server before, and all four images resolve now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_curator/Dockerfile

@@ -14,6 +14,9 @@ FROM dart:3.13.4 AS build
 WORKDIR /app
 COPY pubspec.yaml pubspec.lock ./
 COPY tool/workspace_only.sh tool/
+# The root's dependency_overrides name these by path; pub refuses a path
+# that isn't there, though the curator uses none of them.
+COPY third_party third_party
 COPY apps/learn/halkyon_learn_curator apps/learn/halkyon_learn_curator
 
 # The workspace root with only the curator package, as the server's Dockerfile does it