Force click>=8.1 and litellm to unblock HF Spaces build

HF base image pins click<8.1 which prevents litellm from resolving.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

requirements.txt

@@ -1,3 +1,5 @@
+click>=8.1
+litellm
 a-simple-llm-harness @ git+https://github.com/chuckfinca/a-simple-llm-harness.git
 e2b-code-interpreter>=2.5
 huggingface-hub