document where feedback is saved

CLAUDE.md

@@ -248,6 +248,31 @@ When a user uploads a FIT/GPX/TCX file the server may keep the source in `{user_
 
 For Strava sync, `store_originals=true` causes `POST /api/strava/sync` to save `{"meta":…,"streams":…}` JSON per activity to `{user_dir}/originals/strava/{activity_id}.json`.
 
+## Feedback storage
+
+User feedback submitted via `/feedback/` is stored as flat files under the instance data root (NOT inside a user's own data dir):
+
+```
+{data_root}/
+  _feedback/
+    {handle}.json          ← append-only list of submissions for that user
+    {handle}/
+      {timestamp}_{token}_{filename}   ← attached images
+```
+
+Each entry in `{handle}.json`:
+```json
+{ "id": "1712345678_ab12cd34", "handle": "brut", "submitted_at": "...", "text": "...", "images": ["..."] }
+```
+
+To read feedback on the VPS:
+```bash
+cat /var/bincio/data/_feedback/brut.json | python3 -m json.tool
+ls  /var/bincio/data/_feedback/brut/   # attached images
+```
+
+There is no admin UI for feedback — it is intentionally read via SSH/shell only.
+
 ## About pages
 
 Static public pages at `/about/` (EN), `/about/it/` (IT), `/about/es/` (ES), `/about/ca/` (CA). All use `public={true}` to bypass the auth wall. Each page: