model : add Jina Embeddings v5 Nano (partial EuroBERT) support (#19826)

* WIP: Add EuroBERT support with autoformatting changes

This commit includes:
- EuroBERT model implementation for GGUF conversion
- C++ backend support for EuroBERT architecture
- Unintended autoformatting changes to Python files

Saving before reverting formatting-only changes.

* feat: add back eos assert when not last token pooling

* feat: removed duplicated code and cleanup

* feat: removed not working architectures and unnecessary check

* fix: typo

* fix: dynamic pooling config

* feat: added an example model for eurobert

* feat: proper llama-vocab implementation for jina-v5

* fix: removed unnecessary comments

tools/imatrix/imatrix.cpp

@@ -912,7 +912,9 @@ static bool compute_imatrix(llama_context * ctx, const common_params & params, c
 
     const bool add_bos = llama_vocab_get_add_bos(vocab);
 
-    GGML_ASSERT(!llama_vocab_get_add_eos(vocab));
+    if (llama_pooling_type(ctx) != LLAMA_POOLING_TYPE_LAST) {
+        GGML_ASSERT(!llama_vocab_get_add_eos(vocab));
+    }
 
     auto tim1 = std::chrono::high_resolution_clock::now();
     LOG_INF("%s: tokenizing the input ..\n", __func__);