docs(todo): R2 system follow-up backlog

Captures remaining R2 work after the upload audit + object-cleanup increments:
credential-security review, bucket/custom-domain provisioning audit, CDN purge
integration, and follow-ups to the cleanup work (generic-S3 cleanup, all-versions
delete cleanup, edit thumbnail cleanup). Plus the Vercel production-branch parking
lot item.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

todo/TODO_2026-06-16_r2-followups.md

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+# TODO — Cloudflare R2 system follow-ups (2026-06-16)
+
+Backlog from the R2 audit. Branch: `unstable` (promote down to beta/main later).
+
+## Done (for context — don't redo)
+- [x] Upload audit #1 — content-address storage keys (no URL-first overwrite) — `066d98fe`
+- [x] Upload audit #2 — "Analyzing" status during pre-upload hashing — `6b603cc2`
+- [x] Upload audit #3 — flag/log optimistic (unconfirmed) relay publishes — `ac1dcff1`
+- [x] Upload audit #4 — fail fast on 0-byte files — `04ae0ec4`
+- [x] Upload audit #5 — surface thumbnail/.torrent upload failures — `3d6ffe99`
+- [x] R2 object cleanup on **delete** (`R2Service.deleteVideoStorage`) — `95b51b6e`
+- [x] R2 object cleanup on **edit** (URL replaced) — `33c701aa`
+
+## Open — R2 areas not yet audited/built
+
+### 1. Credential security review (highest priority)
+- [ ] Audit how browser-held S3/R2 keys are stored in IndexedDB (the README's own warning).
+  - Files: `js/services/storageService.js`, `js/r2.js` (legacy settings), `js/ui/profileModal/ProfileStorageController.js`.
+  - Check: encryption at rest, unlock/lock model (`storageService.isUnlocked`), in-memory exposure window, what `resolveConnection` returns when locked, whether secrets can leak to logs/telemetry.
+  - Confirm the "trusted operator only" assumption is actually enforced/communicated in the UI.
+
+### 2. Bucket / custom-domain provisioning
+- [ ] Audit `ensureBucketConfigForNpub` (`r2Service.js`) + `js/storage/r2-mgmt.js`
+      (`ensureBucket`, `putCors`, `attachCustomDomainAndWait`, `setManagedDomain`,
+      `deriveShortSubdomain`) for correctness + failure handling.
+  - Check: Cloudflare management **API token** scope/usage, partial-failure recovery,
+    CORS rule correctness, idempotency, what happens when the user pre-created the bucket.
+
+### 3. CDN purge integration
+- [ ] `scripts/purge-cloudflare-changed.mjs` uses `CLOUDFLARE_ZONE_ID` + `CLOUDFLARE_API_TOKEN`
+      to purge changed `files`. It is **not wired into** the upload/edit/delete flows.
+  - Decide: should publishing a new build / replacing an object trigger a targeted purge?
+  - Note: this is for the *bitvid app* zone, separate from per-user R2 buckets.
+
+## Open — follow-ups to the cleanup work we just shipped
+- [ ] **Generic S3 cleanup**: `deleteVideoStorage` uses `makeR2Client` (R2/path-style).
+      Add a generic-S3 path so `s3UploadService` users' deletes/edits also clean up.
+- [ ] **All-versions delete cleanup**: delete currently cleans the target video's object;
+      superseded versions from *past* edits (pre-`33c701aa`) are not retroactively cleaned.
+      Consider enumerating all cached versions for a `videoRootId` on full delete.
+- [ ] **Edit thumbnail cleanup**: currently skipped to avoid deleting a still-referenced
+      thumbnail. Could diff old vs new thumbnail URL and clean the old one when it changed.
+
+## Unrelated parking lot (from the infra tangent)
+- [ ] Vercel dashboard: set production branch `bitvid-unstable`→`unstable`, `bitvid-beta`→`beta`
+      (so pushes deploy to prod, not preview). Then redeploy `bitvid-unstable` to current HEAD.
+- [ ] Optionally delete the `backup/{beta,main}-pre-unstable-sync` tags once confident.