fix: final review findings — env template placeholder, a11y live region, stale read-only comments

backend/config.py

@@ -24,7 +24,7 @@ VIDEO_ROOT = os.path.abspath(os.environ.get("VIDEO_ARCHIVE", os.path.join(DATA_D
 
 
 def archive_host_paths() -> dict:
-    """Where the archive sits on the host — for the copy-path buttons (REQ-172).
+    """Where the archive sits on the host — for the copy-path buttons (REQ-179).
 
     ponytail: relative VIDEO_ARCHIVE_HOST (./data/archive) cannot be resolved
     inside the container; set it absolute in .env or the buttons stay hidden."""

backend/library.py

@@ -1,7 +1,8 @@
 """The video archive, read as `<video_root>/<date>/<batch>.<ext>` (REQ-010…012).
 
-Read-only by construction: this module only ever lists and stats files, never
-writes into the user's recordings (REQ-074).
+Reads the archive and appends user-initiated uploads and date folders
+(REQ-178); nothing that exists is ever moved, renamed or deleted
+(REQ-163/074 as revised).
 """
 
 import os