fix(admin): library row button renamed 'Scan' -> 'Force Rescan', per owner

Owner ruling that closed the scan-semantics discussion: the code is
correct (per-library scan IS a force scan — hx-vals force:true since
706be09d), but the label hid that. Now the naming invariant holds
everywhere: anything with Force/Rescan in its name re-reads everything
in its scope; plain 'Scan' only exists at folder scope ('Scan this
folder', shallow) and in auto mode. Book-level Rescan verified as the
per-item force path (extractMetadata re-reads sidecars/tags regardless
of file size; recomputeHashInfo follows) — it is the documented answer
to 'I changed this book's sidecar'.

Glossary Scan entry replaced with Force Rescan (old label kept in also:),
scanning.md table + prose pick up the new label. Generated file
regenerated with the Dockerfile-pinned templ version from inside
templates/ so the diff is exactly the label strings.

templates/admin_library.templ

@@ -236,7 +236,7 @@ templ LibraryList(user User, libraries []LibraryData, users []User) {
 								class="btn btn-secondary text-xs px-3 py-1.5"
 							>
 								@Icon("refresh", "h-4 w-4")
-								Scan
+								Force Rescan
 							</button>
 							<button
 								data-lib-id={ library.ID }