fix: add .env and .git exclusions to dockerignore template (#361)

Without these exclusions, docker build silently includes .env files
(which typically contain credentials/API keys) and .git/ history in
the container image. If pushed to a registry, secrets are exposed.

Author: tejaskash

src/assets/container/python/dockerignore.template

@@ -15,6 +15,13 @@ build/
 .coverage
 htmlcov/
 
+# Secrets and environment files
+.env
+.env.*
+
+# Version control
+.git/
+
 # AgentCore build artifacts
 .agentcore/artifacts/
 *.zip