feat(backup)!: exact --images-* matching and --hard-restart-projects

Match --images-no-stop-required and --images-no-backup-required against
the container's exact .Config.Image instead of a substring, so callers
pass full repo:tag references (registry prefix included) and near-miss
image names no longer flip the stop/skip decision. Rename the opt-in
--hard-compose-restart flag to --hard-restart-projects.

The e2e suite pins a SPOT for the DB images and in-container data dirs
(postgres:alpine at /var/lib/postgresql, mariadb:latest at
/var/lib/mysql) and passes exact image refs to the --images-* flags.

BREAKING CHANGE: --images-* now require exact image references, not
substrings; --hard-compose-restart is renamed to --hard-restart-projects.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/e2e/test_e2e_files_no_copy.py

@@ -55,7 +55,7 @@ class TestE2EFilesNoCopy(unittest.TestCase):
             compose_dir=cls.compose_dir,
             databases_csv=cls.databases_csv,
             database_containers=["dummy-db"],
-            images_no_stop_required=["alpine", "postgres", "mariadb", "mysql"],
+            images_no_stop_required=["alpine:3.20"],
             dump_only_sql=True,
         )