test: Update test suite with improved structure

- Update test_helper/common.bash with Docker utilities
- Update unit tests for build, firewall, and security
- Update integration tests for configuration
- Add simple_test.bats for basic testing
- Fix test assertions and error handling

💘 Generated with Crush

Assisted-by: GLM-4.6 via Crush <crush@charm.land>

tests/security/compliance_test.bats

@@ -1,7 +1,12 @@
 #!/usr/bin/env bats
 # Security compliance tests
 
-load 'test_helper/common.bash'
+# Add bats library to BATS_LIB_PATH
+export BATS_LIB_PATH="/usr/lib/bats-core"
+
+load 'bats-support/load'
+load 'bats-assert/load'
+load '../test_helper/common.bash'
 
 @test "wifi modules are blacklisted in configuration" {
     # This will be tested in the actual built system