AI Implementation feature(917): Category Icons (#65)

docs/index.md

@@ -12,7 +12,7 @@ controls, administrator-managed Markdown blog publishing, and public and
 signed-in blog views.
 
 The docs below are organized by purpose so agents can pull just the slice
-they need. Last regenerated 2026-07-23T15:46:55Z.
+they need. Last regenerated 2026-07-23T16:10:00Z.
 
 # Architecture
 
@@ -25,6 +25,10 @@ they need. Last regenerated 2026-07-23T15:46:55Z.
   + signal stores).
 * [Key Files Index](/architecture/key-files.md) - One-line summary of every
   important source file in the repository.
+* [System Category Icon Seed](/architecture/system-category-icons.md) -
+  Idempotent startup hook that writes deterministic 128×128 PNGs for
+  CRY/HW/MSC/PWN/REV/WEB into `UPLOAD_DIR/icons` so freshly cloned
+  instances never serve 404 icons.
 
 # Database