fix: finalize semantic repair and test updates

backend/src/core/encryption_key.py

@@ -1,10 +1,14 @@
-# [DEF:backend.src.core.encryption_key:Module]
+# [DEF:EncryptionKeyModule:Module]
 # @COMPLEXITY: 5
 # @SEMANTICS: encryption, key, bootstrap, environment, startup
 # @PURPOSE: Resolve and persist the Fernet encryption key required by runtime services.
 # @LAYER: Infra
-# @RELATION: DEPENDS_ON -> backend.src.core.logger
+# @RELATION: DEPENDS_ON -> [LoggerModule]
 # @INVARIANT: Runtime key resolution never falls back to an ephemeral secret.
+# @PRE: Runtime environment can read process variables and target .env path is writable when key generation is required.
+# @POST: A valid Fernet key is available to runtime services via ENCRYPTION_KEY.
+# @SIDE_EFFECT: May append ENCRYPTION_KEY entry into backend .env file and set process environment variable.
+# @DATA_CONTRACT: Input[env_file_path] -> Output[encryption_key]
 
 from __future__ import annotations
 
@@ -51,6 +55,8 @@ def ensure_encryption_key(env_file_path: Path = DEFAULT_ENV_FILE_PATH) -> str:
         logger.reason(f"Generated ENCRYPTION_KEY and persisted it to {env_file_path}.")
         logger.reflect("Encryption key is available for runtime services.")
         return generated_key
+
+
 # [/DEF:ensure_encryption_key:Function]
 
-# [/DEF:backend.src.core.encryption_key:Module]
+# [/DEF:EncryptionKeyModule:Module]