Bildschatz: Add public image database website

[sascha11110]

Add a public single-page website that lets anyone search for a word and browse all publicly available images assigned to the matching words.

Enhance the public /api/v2/words/ endpoint with an optional 'search' query parameter that filters words by substring and, when searching, returns all public images of a word (default image plus the images defined on its released unit relations). Search terms have to be at least 3 characters long, otherwise the request is rejected with HTTP
400. Fully backward compatible when no 'search' parameter is given.

Add a lightweight 'bildschatz' Django app serving a responsive single-page frontend that consumes the public API. The search term is read from the 'q' query parameter so result pages are shareable, and the 3-character minimum is enforced inline in the search field.

[deliverino]

LLM Review (verdigado-think)

1. Django correctness

• No model fields were changed or added; the new bildschatz app contains no models, so migrations are not required.
• No paths for creating Job, Unit, or Word objects were introduced.

2. Internationalization

• New strings in lunes_cms/api/v2/views/word_viewset.py and lunes_cms/bildschatz/apps.py are correctly reflected in lunes_cms/locale/de/LC_MESSAGES/django.po.

3. Type safety

• New functions and methods in lunes_cms/bildschatz/views/index.py and the new test suite are fully type-annotated.

4. Code quality gates

• Formatting follows project standards (Black).
• The # pylint: disable=unused-argument in tests/api/v2/test_word_search.py is justified as it refers to a fixture used for its side effects (database loading), following existing test patterns.

5. Security

• Input validation for the search term length (MIN_SEARCH_LENGTH = 3) is correctly implemented both on the backend in WordViewSet.get_queryset and the frontend in bildschatz.html, preventing potentially expensive over-broad queries.

6. Testing

• The new API behavior is thoroughly covered by the new test file tests/api/v2/test_word_search.py.

8. Commit message style

• Incorrect casing: The commit message Bildschatz: Add public image database website violates the repository convention. The summary after the colon must be lowercase (e.g., Bildschatz: add public image database website).

[f1sh1918]

Looks and works already really good @sascha11110
What i recognized is

1. I think there should be a x button to delete search query as its standard IMO
2. Not sure what image export quality we want but the current resolution is super low, is that intended. Not sure actually what resolutions we currently have

[f1sh1918]

please also test how to test section @sascha11110

[LeandraH]

This looks very cool! One thing, I tested with a word that also has an image for the unit word relation, and those images didn't show up. I guess we should show those words as well.

[LeandraH]

Let's not send Google our data 😬