a /plugins screen to install, enable, disable and uninstall

the management surface for what the last commit made possible. two panels either
side of a selection that lives in ?selected= and is read by both independently,
so neither can be telling the other something stale — rows are real Links, not
buttons holding the name in a closure.

the detail panel shows what the tree declared (api, schema, sidecar, web),
because "installed and nothing happened" is otherwise a mystery, and it names
what uninstall does NOT do: neither disable nor uninstall deletes anything the
plugin stored, and the screen says so rather than leaving someone to guess
whether a button destroys their data.

a directory whose manifest will not parse is listed with its error rather than
skipped. a malformed plugin that simply does not appear is indistinguishable
from one nobody wrote.

`outdated` is surfaced as an Update button: the version on disk moving after an
install is the normal state on a developer's machine, and it should be visible
rather than inferred.

the four mutations are written out rather than generated in a loop — useMutation
is a hook, and a hook called from inside a helper is a rules-of-hooks violation
even when the call order happens to be stable. caught before it shipped.

verified against a running server: the spa builds (19.8 MB bundle containing the
new screen), / serves 200, /api/plugins answers authenticated and 401s without a
token. full suite 719 pass, same 10 pre-existing failures. live server and
plugin_installs left untouched.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/apps/officer-web/App.tsx

@@ -64,6 +64,7 @@ export function App() {
             <Route path="/photos" element={<Dashboard.PhotosScreen />} />
             <Route path="/photos/:section" element={<Dashboard.PhotosScreen />} />
             <Route path="/app-store" element={<Dashboard.AppStoreScreen />} />
+            <Route path="/plugins" element={<Dashboard.PluginsScreen />} />
             <Route path="/jellyfin" element={<Dashboard.JellyfinScreen />} />
             <Route path="/jellyfin/:section" element={<Dashboard.JellyfinScreen />} />
             <Route path="/transmission" element={<Dashboard.TransmissionScreen />} />