feat(achievements): rebuild the page as a trophy cabinet with hints

Replace the card grid with medals, a showcase, category shelves, a record book and a
detail sheet. Add GET /achievements/hints, which explains how to unlock what is still
locked from the user's own library and reading history, backed by a new page-count
index. Year-Round Reader now reports its months read as progress.

server/test/e2e/authorization-matrix/route-inventory/manifest.json

@@ -1,7 +1,7 @@
 {
-  "totalRoutes": 650,
+  "totalRoutes": 651,
   "byPermission": {
-    "(none)": 282,
+    "(none)": 283,
     "Permission.ManageMetadataConfig": 38,
     "Permission.EmailSend": 34,
     "Permission.LibraryEditMetadata": 35,