chore: release SAC 0.5.0

Bump version, document security hardening in README, add github snapshot
push script with URL/login/IP sanitization for public mirror.

backend/app/version.py

@@ -1,5 +1,5 @@
 """Единый источник версии SAC (API, health, логи, OpenAPI)."""
 
 APP_NAME = "Security Alert Center"
-APP_VERSION = "0.4.15"
+APP_VERSION = "0.5.0"
 APP_VERSION_LABEL = f"{APP_NAME} v.{APP_VERSION}"

backend/tests/test_health.py

@@ -4,6 +4,6 @@ from app.version import APP_NAME, APP_VERSION, APP_VERSION_LABEL
 
 
 def test_version_constants():
-    assert APP_VERSION == "0.4.15"
+    assert APP_VERSION == "0.5.0"
     assert APP_NAME == "Security Alert Center"
-    assert APP_VERSION_LABEL == "Security Alert Center v.0.4.15"
+    assert APP_VERSION_LABEL == "Security Alert Center v.0.5.0"