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.

docs/admin/scanning.md

@@ -36,7 +36,7 @@ Every scan is one of two kinds:
 | Control | Where | Kind | Scope |
 | --- | --- | --- | --- |
 | **Force Rescan All Libraries** | Admin dashboard → Quick Actions | Force | Every library |
-| **Scan** (library row) | Admin → Libraries | Force | That library |
+| **Force Rescan** (library row) | Admin → Libraries | Force | That library |
 | **Scan this folder** (folder-row icon) | Admin → Libraries → a library's panel | Shallow | That folder's subtree |
 | **Auto-Scan** + **Scan Interval (seconds)** | Admin → Settings → Scanning | Shallow | Every library |
 | **Retry** / **Retry all** | Admin → Libraries → Processing Issues | Per-item | Failed items only |
@@ -48,8 +48,8 @@ The details behind the table:
   force scan job for each. Libraries that already have a scan running are
   left alone — the button reports which libraries started and which were
   skipped because a scan was already in flight.
-- **Scan** on a library row is the same force rescan, scoped to that one
-  library. It shares the dashboard button's semantics exactly.
+- **Force Rescan** on a library row is the same force rescan, scoped to
+  that one library. It shares the dashboard button's semantics exactly.
 - **Scan this folder** is the only folder-sized scan, and the only shallow
   one an admin triggers by hand: unchanged files are skipped, and only
   that folder's subtree is walked. Because a partial scan can't vouch for