docs: revise REQ-074 read-only wording for user-initiated uploads

docs/requirements.md

@@ -360,4 +360,6 @@ changes.
   (video archive, data folder) is configured through environment/volumes — never hardcoded.
 - **REQ-073** — The health endpoint reports: detected device/GPU, ffmpeg availability,
   whether the HuggingFace token was picked up, and database reachability.
-- **REQ-074** — The system never writes anything into the user's video archive folder.
+- **REQ-074** — The system writes nothing of its own into the user's video archive folder:
+  no outputs, moves, renames or deletions; only user-initiated uploads and folder creation
+  (REQ-178) append to it.