server : honor --embd-normalize CLI arg (#23125)
The --embd-normalize flag was registered only for the embedding and debug
examples, so llama-server rejected it and the /embedding handler used a
hard-coded default of 2 (L2). Add LLAMA_EXAMPLE_SERVER to the flag's
example set and read params.embd_normalize as the handler's default. The
per-request "embd_normalize" body field continues to override.
