fix(gallery): correct gemma-4 model URIs returning 404 (#9379)

The gemma-4-26b-a4b-it, gemma-4-e2b-it, and gemma-4-e4b-it gallery
entries pointed at files that do not exist on HuggingFace, so LocalAI
fails with 404 when users try to install them.

Two issues per entry:
- mmproj filename uses the 'f16' quantization suffix, but ggml-org
  publishes the mmproj projectors as 'bf16'.
- The e2b and e4b URIs hardcode lowercase 'e2b'/'e4b' in the filename
  component. HuggingFace file paths are case-sensitive and the real
  files use uppercase 'E2B'/'E4B'.

Updated filename, uri, sha256, and the top-level 'mmproj' and
'parameters.model' references so every entry points at a real file
and the declared hashes match the content.

Verified each URI resolves (HTTP 302) and each sha256 matches the
'x-linked-etag' header returned by HuggingFace.

Signed-off-by: Matt Van Horn <mvanhorn@gmail.com>