Update the roadmap for cacheable media and session-only completions

ROADMAP.md

@@ -20,6 +20,13 @@ they land.
   - [x] Tag cloud in the sidebar (click to search, hidden from guests for
         blacklisted items)
   - [x] Status filter (matched / not_found / deleted / custom / unknown)
+- [x] **Cacheable media serving**
+  - [x] Stable signed URLs (7 d TTL, 24 h rotation) plus a `v=<md5>` cache
+        buster, so replacing a file under the same J-ID invalidates it
+  - [x] ETag/Last-Modified and a private `Cache-Control` (immutable for
+        versioned media), conditional 304s
+  - [x] Real 480 px image thumbnails (cached by MD5) instead of serving
+        full-size originals through the thumbnail endpoint
 
 - [x] **Random image** endpoint and page: `GET /api/random/` (aliases
       `/random`, `/random/`) with `rating=s,q,e` filters; fastfetch mode
@@ -104,12 +111,16 @@ Files now stage first and are resolved before entering the library.
         shell indicator; rate-limited runs retry with backoff
   - [x] Perceptual-hash comparison against the library, loaded once per batch
   - [x] IQDB candidates stored with one batched enrichment request
+  - [x] Indexed uploads are announced through a bounded per-run feed and the
+        staged row is deleted; nothing persists on the board to dismiss
 - [x] **Upload UI**
-  - [x] Three-column board: Pending & Unmatched / Visual Similarity Detected /
-        Auto-uploaded & Indexed, private per user (staff included)
+  - [x] Four-column board: Pending & Unmatched / Visual Similarity Detected /
+        Auto-uploaded & Indexed (session feed) / Failed, private per user
+        (staff included)
   - [x] Metadata modal (link to e621 post, IQDB candidates, custom metadata)
   - [x] Per-file progress plus background pipeline status
-  - [x] Bulk actions: bulk rate, discard all (pending/visual), dismiss all
+  - [x] Bulk actions: bulk rate and discard all (chunked past the API's
+        1000-id cap)
 
 ## 4. Staff tools