feat(issues): Processing Issues page retry UI with a sequential client queue

Per issue card: a Retry button — error-severity issues previously had no
action at all (only warning/info got Dismiss). Right of the Errors stat
card: Retry all, which builds a queue of every issue currently on the
page and runs them strictly one at a time through the per-issue retry
endpoint. The browser is the queue — resource use is bounded to a single
book in flight, and no batch endpoint exists to maintain.

While the queue runs, the button shows an n/m counter and cards tint via
client-local state classes (the sanctioned island shape; the cards
themselves stay templ-rendered). After the queue drains, the page swaps
in the new /admin/libraries/:id/issues/content templ partial — the
unlinked-books htmx.ajax pattern with a reload fallback — so resolved
issues drop off server-side while failures remain listed, with a
summary toast and per-item error toasts carrying the real failure
reasons.

CSP discipline holds throughout: Alpine @click component methods, no
inline handlers, no js:-prefixed hx-vals.

web/src/main.ts

@@ -22,6 +22,7 @@ import "./library-switcher";
 import "./linking";
 import "./login";
 import "./password_validation";
+import "./processing_issues";
 import "./profile";
 import "./profile-modal";
 import "./register";