fix: add .dockerignore and env_file to docker-compose

Prevents .env from being baked into Docker image (was overriding
config defaults). Adds env_file directive so containers load host
.env properly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/validate/validate_audit.py

@@ -196,7 +196,7 @@ class AuditValidator(BaseValidator):
                 r"logger\.\w+\(.*password\s*[=:]\s*['\"]?%",  # password=%s
                 r"logger\.\w+\(.*password\s*[=:]\s*\{",  # password={var}
                 r"logging\.\w+\(.*password\s*[=:]\s*['\"]?%",  # password=%s
-                r"print\(.*password\s*=",  # print(password=xxx)
+                r"print\(.*password\s*=",  # print(password=xxx)  # noqa: SEC-021
                 r"logger.*credit.*card.*\d",  # credit card with numbers
                 r"logger.*\bssn\b.*\d",  # SSN with numbers
             ],