fix(frank-default-large): enable flash attention by pairing V cache to q8_0

Root cause of ~1 t/s long-context decode: llama.cpp build has
GGML_CUDA_FA_ALL_QUANTS=OFF, and FA requires K type == V type.
Mixed cache q8_0/f16 silently disabled FA, collapsing decode at
200k ctx. Set V to q8_0 (halves V memory too) and retune
threads 12/1 for 16 Zen5 cores.

scripts/serve-llama-frank-large.sh

@@ -34,11 +34,11 @@ fi
 : "${DEVICE:=ROCm0}"
 : "${N_GPU_LAYERS:=all}"
 : "${CACHE_TYPE_K:=q8_0}"
-: "${CACHE_TYPE_V:=f16}"
+: "${CACHE_TYPE_V:=q8_0}"
 : "${BATCH_SIZE:=2048}"
 : "${UBATCH_SIZE:=512}"
-: "${THREADS:=8}"
-: "${THREADS_HTTP:=8}"
+: "${THREADS:=12}"
+: "${THREADS_HTTP:=1}"
 
 LLAMA_SERVER="${LLAMA_SERVER:-/home/dank/llama.cpp/build/bin/llama-server}"
 MODEL="$MODEL_DIR/$MODEL_FILE"