Add safe optimization flags to gemma4 + qwen36 (fastsafetensors, prefix-caching, fp8 kv)

Aligned with sibling recipes in eugr/spark-vllm-docker. Applies on next swap to each model.
First real swap gemma4 -> qwen36 succeeded in 5:30 with --moe_backend=flashinfer_cutlass.

models.yaml

@@ -39,6 +39,9 @@ models:
       - --reasoning-parser=gemma4
       - --tool-call-parser=gemma4
       - --enable-auto-tool-choice
+      - --load-format=fastsafetensors
+      - --enable-prefix-caching
+      - --kv-cache-dtype=fp8
 
   qwen36:
     display_name: "Qwen3.6 35B-A3B (daily driver)"
@@ -52,6 +55,9 @@ models:
       - --max-model-len=65536
       - --reasoning-parser=qwen3
       - --moe_backend=flashinfer_cutlass
+      - --load-format=fastsafetensors
+      - --enable-prefix-caching
+      - --kv-cache-dtype=fp8
 
   qwen3-235b-fp8:
     display_name: "Qwen3 235B-A22B FP8 (legacy)"