chore: Add hadolint config to ignore version pinning warnings

DL3008 and SC2016 are ignored because:
- Pinning apt package versions creates maintenance burden
- System packages are upgraded for security (apt-get upgrade)
- Echo statements for nginx config are properly escaped
- These checks are too strict for our use case

Author: bobbyonmagic

.hadolint.yaml

@@ -0,0 +1,7 @@
+---
+ignored:
+  - DL3008  # Pin versions in apt-get install
+  - SC2016  # Shell expansion in echo statements
+
+trustedRegistries:
+  - docker.io