Add .gitattributes: LF in the repository, CRLF for batch files

Normalize the files that had been committed with CRLF (line endings only,
no content changes).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/alembic.ini

@@ -1,24 +1,24 @@
-[alembic]
-script_location = migrations
-prepend_sys_path = .
-
-[loggers]
-keys = root
-
-[handlers]
-keys = console
-
-[formatters]
-keys = generic
-
-[logger_root]
-level = WARN
-handlers = console
-
-[handler_console]
-class = logging.StreamHandler
-args = (sys.stderr,)
-formatter = generic
-
-[formatter_generic]
-format = %(levelname)-5.5s [%(name)s] %(message)s
+[alembic]
+script_location = migrations
+prepend_sys_path = .
+
+[loggers]
+keys = root
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+
+[handler_console]
+class = logging.StreamHandler
+args = (sys.stderr,)
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s