fix(build): add .dockerignore + safe probe — fix docker build failure

Build was failing, likely due to:
1. 165MB build context (no .dockerignore) — cccl_upstream/ 53MB, zip 97MB
2. probe_corex_api.py used importlib.import_module which may init CUDA
3. pip install without --timeout could hang on unreachable mirror

Fixes:
- .dockerignore: excludes cccl_upstream/, vllm/, *.zip, docs/ etc
  Build context: ~2MB instead of 165MB
- probe_corex_api.py: rewritten to use ONLY ast.parse, zero runtime imports
- pip install: added --timeout 30

.dockerignore

@@ -0,0 +1,17 @@
+# Exclude everything not needed for the Docker image
+cccl_upstream/
+vllm/
+muh/
+docs/
+optimizations/
+vllm_adapter/
+*.zip
+*.txt
+*.md
+*.json
+*.muh
+.git/
+.gitignore
+__pycache__/
+*.pyc
+# Keep: qwen3_6_scripts/, computility-run.yaml, Dockerfile, launch_service