fix(ui): cookie-authed users' writes silently stranded behind bearer gates

THE CLASS: the /api JWT middleware's TokenLookup is
"cookie:token,header:Authorization:Bearer" — the token cookie always
rides same-origin fetches, so a signed-in user never needs the
localStorage bearer. But a dozen call sites gated their fetch on
`localStorage.getItem("token")` and early-returned when absent. The
global 401 interceptor CLEARS that localStorage entry on any session
rotation/blip — after which every gated write silently did nothing:
theme changes reverted on reload (the reported "can no longer change
themes", on top of the interpolation bug d5dbaa48 fixed), chain-order
selects, collection deletion, Add-to-collection submits, filter
save/load/delete, conflict actions, linking actions, stats charts,
tag suggestions, device management, admin scanner actions — all dead
for perfectly authenticated cookie users.

Fix: storage.ts exports authHeaders() (bearer when present, cookie
carries otherwise) and every gate/header site now uses it — theme.ts,
collections.ts (htmx auth, doRemoveBook/doBulkRemove, setChainOrder),
bookPicker submit, filter_builder suggestions + match count,
collection-rules apply hook, bookshelf save/load/delete filter,
conflicts x4, linking x3, admin scanner actions + polls (requireToken
removed — its "Session expired" toast fired for cookie users too),
dashboard preferences/sections, custom-section-builder, header
scanner poll, stats x3, tag suggestions, profile delete-account
(which also wrongly redirected cookie users to /login), and
device-management x4. Reads keep their graceful-empty behavior; the
bearers still ride along when present.

Pinned: the knob-matrix theme spec now REMOVES localStorage.token and
asserts the theme PUT still fires (cookie-only) and the class flips —
the exact strand that started this.

Found by noticing the panel browser's Nord click switched the class
but produced no PUT: the persistence half was gated on a token the
401 interceptor had cleared.

web/src/storage.ts

@@ -39,6 +39,18 @@ function getSelectedLibrary(): string {
   return "";
 }
 
+// Headers for same-origin /api fetches: the localStorage bearer when
+// present, otherwise nothing — the token COOKIE (always sent on
+// same-origin requests) carries auth, since the middleware's
+// TokenLookup checks cookie:token before the header. NEVER gate a
+// call on the bearer's presence: the global 401 interceptor clears
+// localStorage, and token-gated calls then strand every click that
+// should persist ("can no longer change themes", 2026-10-31).
+function authHeaders(): Record<string, string> {
+  const token = localStorage.getItem("token");
+  return token ? { Authorization: `Bearer ${token}` } : {};
+}
+
 function setSelectedLibrary(libraryId: string): void {
   const value = libraryId === "" ? ALL_LIBRARIES : libraryId;
   localStorage.setItem("selectedLibrary", value);
@@ -51,6 +63,7 @@ function clearAll(): void {
 
 export {
   ALL_LIBRARIES,
+  authHeaders,
   clearAll,
   getRefreshToken,
   getSelectedLibrary,